DEMETRIO STRATOS RETHINKS VOCAL TECHNIQUES: A HISTORICAL INVESTIGATION AT ISTC IN PADOVA, Proceeding of the SMC Conference 2011 (Sound and Music Computing), Padova 6-9 July 2011, pp. 48-55.

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Laura Zattra

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Graziano Tisato

Elena Ceolia, Graziano Tisato, Laura Zattra


1 DEMETRIO STRATOS RETHINKS VOCAL TECH- NIQUES: A HISTORICAL INVESTIGATION AT ISTC IN PADOVA Elena Ceolin Graziano Tisato Laura Zattra ISTC (Istituto di Scienze e Tecnologie della Cognizione), CNR, Padova Università di Padova Dipartimento di Storia delle Arti Visive e della Musica Università di Padova Dipartimento di Storia delle Arti Visive e della Musica ABSTRACT Demetrio Stratos ( ) was a singer known for his creative use of vocal techniques such as diplophony, bitonality and diphony (overtone singing). His need to know the scientific explanation for such vocal behaviors, drove him to visit the ISTC in Padova (Institute of Cognitive Sciences and Technologies) in the late Seventies. ISTC technical resources and the collaboration with Franco Ferrero and Lucio Croatto (phonetics and phoniatric experts), allowed him to analyze his own phonoarticulatory system and the effects he was able to produce. This paper presents the results of a broad historical survey of Stratos research at the ISTC. The historic investigation is made possible by textual criticism and interpretation based on different sources, digital and audio sources, sketches, various bibliographical references (published or unpublished) and oral communications. Sonograms of Stratos exercises (made at the time and recently redone) show that various abilities existed side by side in the same performer, which is rare to find. This marks his uniqueness in the avant-gard and popular music scene of the time. The ultimate aim of this study was to produce a digital archive for the preservation and conservation of the sources related to this period. 1. INTRODUCTION Efstratios Demetriou (April 22, 1945 June 13, 1979), better known as Demetrio Stratos, was a multiinstrumentalist, music researcher and singer. He is known for his activity with the Italian progressive rock group Area, as well as for his collaborations with other artists and his solo activity. His interests in ethnomusicology and extra-european traditions, the complete mastery of a wide range of vocal techniques and the awareness of the spoken language constraints, were his background. That induced him to free the voice from the linguistic superstructures and to explore the underlying sonic substance. Among the most Copyright: 2011 Ceolin et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. impressive results of his research on what he called the instrument-voice [1], a series of unbelievable performances must be mentioned, mainly in the whistle register, producing two or three inharmonic partials at the same time, in a frequency region that could reach the 8,000 Hz. During the late Seventies, Stratos visited several times the ISTC of CNR (Consiglio Nazionale delle Ricerche) in Padova ( Here, he worked with the physicist Franco Ferrero, who was an expert in phonetics, and with Lucio Croatto, phoniatric expert, to explore this vocal effects by the means of ISTC technical resources: a spectrograph of the VoiceIdentification and an electroglottograph (or EGG, or laryngograph) Elettro-Glottograph EG 830 by the F-J Electronics [9]. Unfortunately, Stratos premature death at age 34 put an end to his research activity, which would have provided other results and assertions to his original view and definitely future pedagogical and scientific outcomes. Why, thirty years after his death, the myth of Demetrio Stratos voice is still alive and growing? His unusual extension of vocal techniques, the musical use of his vocal features and his penchant for scientific research, show the emergence of a figure in the musical scene who struggles against established vocal techniques and monody, but also against the established music industry. What was Stratos looking for from phonetics, physicists, and phoniatric experts? In what way did he try to study his ability to obtain such complicated techniques? This paper is an attempt to reply to this double question. The investigation starts from two premises. The first one is the necessity to study the Stratos scientific experience through the sources, an aspect which has not yet been considered by literature. Literature normally has a target audience from the rock ambience. Stratos should be considered more broadly for his scientific contribution. His Paduan period is significant for this reason. It is a particular case where creativity rethinks science, as happened worldwide in the musical and scientific research centers (San Diego, Stanford Universities, Ircam, CSC in Padova, etc.). The Seventies drove musicians and scientists to collaborate in order to understand how voice and instruments physically worked (think e.g. the spectral analysis and physical models research, etc.). In this case, the performer himself decides to study his own voice and be more acquainted with his own capabilities.

2 The second premise emphasizes the problem of music conservation and preservation. The ISTC shares the same problem musical archives or musical institutions have. Oblivion or inaccurate preservation exist because of scientists and musicians continued acquisition of knowledge and the urge of experimentation, that brought to postpone, and often to forget, the organization and preservation of their musical materials [2, 3]. Together with the reconstruction of Stratos experience, this research has been based on the philological method, in which the researcher follows different steps in his investigation. First of all the philologist aims to the complete recension and description of extant sources (even oral witnesses). Then he proceeds listing all different sources and name them with abbreviations derived from their content or origin. XX century music is characterized by heterogeneous sources (audio and video sources, sketches, digital sources, spectrograms and/or digital scores or description, oral witnesses) therefore he must consider all of them. The accurate description of the sources is the third moment of the investigation [4]. Section 2 gives an overview of the historical experience. Section 3 describes Ferrero and Stratos work during the recording and the analysis of the vocal effects. Section 4 describes sources, methodological problems and the organization of the new archive with Stratosrelated materials at the ISTC [5]. 2. STRATOS AT THE ISTC ( ) This section tells the story of Stratos presence at the ISTC, as derived from the sources mentioned in chapter A necessity Many are the reasons why Stratos had found the necessity to analyze his own voice compelling. First of all, as it is stressed by all Area members, Stratos background was a melting pot of Greek, Egyptian and Balcanic musical traditions. Another field which certainly caused this interest were infant and newborn voices. Daniela Ronconi, Stratos wife, told that Stratos was fascinated by his daughter Anastasia s voice, especially during the lallation phase; 1 he kept asking himself the reason why people lose this interesting capability while they grow up [6]. Another fact happened in 1974, when Stratos performed the John Cage piece Sixty-two Mesostics Re Merce Cunningham (1971) for voice unaccompanied using a microphone, a score that demands the performer a great independence and liberation. The occasion to meet Tran Quang Hai, a renowned interpreter of Eastern musical tradition and harmonic chant, was also important and allowed Stratos to learn this way of singing and its philosophical implication. Finally, Nicola Bernardini had a relevant part in Stratos experience. Bernardini (at the time a member of Prima Materia) met Demetrio Stratos and exchanged discussions. They used to perform overtone singing compe- 1 The infant baby s gibberish (from Latin lallāre: to sing lullaby, a verb containing the concept of producing alliterative sounds). In phonetics it means more generally a defect of speech (replacement of L for R). titions («we travelled together a lot at the time, and practicing the overtone singing was the best pastimes!» [17]). 2.2At the ISTC The musical experimentation was not enough for Demetrio Stratos. He needed to give a scientific explanation to the phono-articulatory phenomena. This is why he firstly asked Pino Sambataro, his reliable otorhinolaryngologist in Milan to study his voice. But because of his inability to understand how Stratos voice worked, this doctor decided to contact a colleague in Padova, Maurizio Accordi, who was in his opinion a specialist in this field. Accordi and Lucio Croatto, director of the ISTC (at the time Centro per le Ricerche di Fonetica) examined Stratos phono-articulatory system accurately, and found nothing unusual. No special instrumentation was used, but only a laryngeal little mirror, for the videolaringostroboscopy did not exist yet. Then they thought to examine Stratos voice also from an acoustical point of view, and take him to the ISTC [6]. This happened during Fall 1976, which is also confirmed by [5] and the researcher and physicist Kyriaki Vagges, who worked at the time with Ferrero at the ISTC, and is the sole witness alive of that meeting [8]. During their meetings, Ferrero and Stratos recorded several improvisations, which were analyzed to observe their spectral content (several papers were published under the names of Accordi, Croatto and Ferrero). Unfortunately, it is difficult to date those meetings, and yet material sources (audio sonograms and paper sources) do not give any help. Nonetheless it is certain that Stratos went to the ISTC ISTC during the years 1976, 1977 and 1978 (daa-ssn, daa-d, 2 and [12]) and in 1999 Ferrero declared to Janete El Haouli that he worked with Stratos at the ISTC for 4 or 5 times [1: 129]. Audio sources and sonograms demonstrate that most of the vocal material was recorded at the ISTC. Only a small number of audio recordings were made at Stratos home [6]. Since evidently no electroglottograph tracks exist of those materials, it is easy to establish which vocal effects were recorded at ISTC under monitored conditions. 2.3Recording Demetrio Stratos Speech and glottic sources were recorded by Ferrero team in the ISTC silent room, respectively on a Revox A77 tape recorder, and an Electro-Glottograph EG 830 by F-J Electronics [8]. The equipment also included an oscilloscope for the real time visualization and the signal analysis [8]. The vocal and glottal signals were recorded on two separate synchronous tracks. The speech signal was captured from a microphone at 10 cm from the mouth. The glottic source was acquired by means of two electrodes, attached to both side of the neck, in correspondence of the larynx. This allowed to pick up the rough signal of the vocal cords, not filtered by the resonances of the vocal tract. The absence of articulatory effects takes away all 2 The sources are listed in chapter 4.2.

3 intelligibility and all human characteristics from the sound, and makes it like a buzzing of a reed instrument. The subsequent analyses were made on a massive Voiceidentification Spectrograph 700 (same machine used in forensic application) by Franca Zecchin, who did the very first study of those materials [9]. The maximum frequency band the machine could capture was 8 KHz, which explains why Ferrero-Zecchin analysis established that Stratos could perform some extraordinary bitonality effects reaching 7000 Hz [12]. However, today analysis (made in 2002) has allowed to determine that Stratos maximum was much higher, of about 8000 Hz (Fig. 3). 3. VOCAL EXERCISES AND ANALYSIS 3.1Stratos original vocal technique Stratos ability allowed him to produce diplophony, bitonality and diphony (overtone singing) [10]. 3 Diplophony is the ability to make two sounds at the same time. Vocal cords vibrate asymmetrically, and produce a waveform period with normal amplitude followed by a feebler one. One cannot always perceive two separate sounds: a normal period followed by an anomalous period means that the perceived frequency is one octave lower (for psycoacoustic reasons it is sometimes difficult to distinguish). If two normal periods are followed by one abnormal, the pitch of the perceived sound results an octave and a fifth lower [10]. What is heard, consequently, is a dirty and scratched voice, because two frequency components fall in the same critical band and because of the masking of the lower partials above the higher. If this phenomenon can be sometimes accidental in the pathological voices and sometimes also in singing, Stratos made it intentionally. Bitonality is the unusual capability to produce two different sounds which are sometimes not in a harmonic relation. In normal conditions, the vocal folds produce a sound with harmonic spectral components, i.e. the frequencies of partials are multiple of a fundamental, or separated by the same frequency interval. Sometimes the contraction of false vocal cords provokes a second sound due to the low frequency modulation. Some other times, strong false vocal cords contractions trigger very high whistles. In the case of bitonality, the adduction of vocal cords is so strong that it generates two independent nonharmonic sounds, as it happens when you touch with a finger the string on a musical instrument and the original sound splits in two. In some of Stratos effects, the EGG demonstrated the absence of the vocal cords vibration: in this case, the perceived pure high frequency whistles are due to the reduced dimension of pharyngeal resonators [10]. Overtone singing is the extraordinary way to split the harmonic partials of a vocal sound, normally fused in a single one, in two distinct sonic images: one in the usual vocal range of the singer, the other in an high or very high register; this pure and flute-like sound corresponds to one of the harmonic partials reinforced by the resonances or formants of the spectral envelope. In enhancing the harmonic partial, one can create real melodies. An overtone singer can play these harmonic pitches in a scale which is a natural pentatonic scale (see Zarlino) [10]. 3.2Analysis and Sonograms Analyses of Stratos voice are mentioned in the following sources: dav-l, dc-val82, dc-riv80, dc-riv80/cp, dc- T/BATT, dc-t/cop, dc-ce/cnr, dc-son, dc-t/zecc (see Table 2). Franca Zecchin s graduation thesis is the first study dedicated to Stratos vocalizations. It is a very significant source because it was made during the period in which Stratos came at the ISTC [9, 11], and because it allows establishing the origin and reliability of the audio sources. In this way it is possible to verify that nearly all Stratos vocal effects were recorded at ISTC in controlled conditions, and cannot be the result of a (fraudulent) mixing, filtering, etc. From the entire series, Ferrero s team selected a set of 22 vocalizations to be the most representatives. The thesis reports that examples from n.1 to n.18 were recorded at the CNR during the fall Vocalizations nn. 19, 20, 21 were brought by Stratos in September 1977, pre-recorded on a tape. Vocalization n. 22 was recorded during the Fall 1976 [9]. All those examples were subjected to analysis, even if some of them (nn. 1-6 and 12, 15, 16) do not appear in Zecchin s thesis nor in the published article [9] (Zecchin also does not mention vocalizations nn. 7 e 11). The electrographic track of vocalizations nn. 8-10, 13, 14, 17, 18 is completely flat because of the absence of the vocal folds vibration. The thesis also includes a brief description of Stratos phono-articulatory attitude during the vocalization, but not the way it was deduced. Unfortunately, after 30 years, Zecchin does not remember the methodology they adopted. She makes two assumptions: the described vocalization mechanism could be a deduction made a posteriori, through the study of the sonograms and the formant positions and movements. A more likely explanation could be that Ferrero discussed with Stratos about what he felt inside his phono-articulatory system, and compared this sensations with the sonographic results [11]. Figure 1 shows the analysis of fragment n. 18, as it is shown in the article made in 1980 [12]. It begins with 2 whistles of 3700 Hz (and 2 nd harmonic, small triangle) and 5000 Hz (empty triangle). 3 Vocal analysis is one of Graziano Tisato s research topic, started during the Seventies. Soon after Stratos Paduan period, Tisato met Ferrero, and decided to determinate a precise terminology for the vocal effects. These were published in [14]. In 1989 Tisato realized the first model synthesis for the overtone singing [18].

4 V O C A L I Z E N THESIS -Phono articulatory attitude: the same as in nn. 8, 9 and 13. Spectrographic Recording -Cue: two non harmonic whistled notes, one at 3700 Hz + 2, the other as pure sound beyond 5000 Hz. Their frequency is decreasing. -1st s: transition phase after which they continue as pure sound with non harmonic fluctuations. Whistled bitonal sound. -2nd – 3rd s: a whistle overlaps for three times with a fundamental frequency at 1660 Hz + 2nd and 3rd, with the result of a three-partite sound. -4th s: the main whistle with a lower frequency disappears. A flat changeable whistle overlaps the whistled note, stabilizing around 1500 Hz: bitonal sound, like bird singing. -5th s: pitch at 1500 Hz + 2nd and flat inflected whistle (like bird singing) between 4000 and 5000 Hz. Figure 1. Vocalization n. 18 [12: 253]. In a graduation thesis made in 2005, Copiello showed new analyses of the 22 examples, which had been made by Tisato [16]. They considered sonograms, pitches and intensities contours [16]. The numeric representation shows unquestionable advantages and it solves those resolution and frequency limits of the Sonograph 700, thanks to the possibility to choose the proper frequency and time scale, and to obtain the parameter values straight from the data analysis. Table 1shows the comparison [16]. Fig. 2 shows the same vocalization of Fig. 1 in an arbitrary time scale. The Fig. 3 shows a sonogram with an example of tritonality STUDY 2005 STUDY Electroglottographic recording: flat during the whole length. (vocalize 18 was recorded in 1976 at CNR. The tape include the verbal vocalize but not the glottic vocalize) (annotations are made only if the analysis is different from the one made in 1977) Spectrographic Recording -During the whole vocalize there is a noise band around 1200 Hz Electroglottographic recording: Not quoted (annotations where different) Spectrographic Recording: -Whistled at ~3555 Hz (La7) and 2nd harmonic; and beyond 5500 Hz pure sound. -1,5 s: the lover whistle loses the 2nd harmonic s: whistle at ~1660 Hz (Sol6) Table 1. Vocalize n. 18: comparison between [12: 253] and the new analyze with modern sonograms [16]. Figure 2. The vocalization starts with a guttural impulsive sound, then it proceeds until 2.2 s with two inharmonic whistles (bitonality case): the lower at Hz presents a second harmonic, the higher slopes down from 5500 to about 4000 Hz. At this point until 3.3 s. a new inharmonic component appears at 1650 Hz to form the tritonality. Around Hz a very narrow noise band can be heard.

5 Figure 3. The vocalization starts with a breathy-vocalized sound of 300 ms, then 600 ms of an expiratory noise of low amplitude. At ~1.4 s, an high pitched cry with a set of 4 harmonics of 1 s can be heard, which raises from ~1100 (DO#6) to 1289 Hz (MI6-). Between 5-8 s, a chirp go down from ~7900 Hz to ~6200 Hz. Between 6-7 s a whistle appears at 4000 Hz and then at 6000 Hz. There is also a colored noise with 2 formants at 500 and 1000 Hz. At 7 s a chirp falling from ~4400 to 2250 Hz. 4. SOURCES 4.1New texts and supports in philology During the past half-century music and musical research (in both popular music and art music) have been made involving new ways of producing and analyzing sounds. As a result, sources that document information of this activity are heterogeneous and very different from the traditional status of paper material [13]. They are not necessarily a visible or symbolic trace and can indifferently be: 1) the audio and video source (analogue, CD, the mini disc, the memory of the computer); 2) printed, handwritten sources; 4) traditional scores; 5) different sketches; 6) articles; 7) oral witnesses (oral communications find justification in the contemporary context where collaboration is important); 8) visual representations such as sonograms [3, 4]. Stratos experience is a good example of a XX century historical event that must be studied in detail in terms of material and oral documentation. Chapter 4.2 shows the list of sources. Oral communications have been indispensable in reconstructing the historical facts and are included in [5]. 4.2Sources at the ISTC and elsewhere Table 2 lists all materials collected during this research project. General Cathegories of sources are: Analogue audio document (daa), Visual analogue document (dav), Paper document (dc), Audiovisual digital document (dda). For specific description, see [5]. SOURCE Cantare la Voce (long play disc) Copia disco dimostrazione Titze, (magnetic tape 1/8, SONY HF-ES60, compact cassette) Demetrio (magnetic tape 1/8, BASF Chromdioxid 90, compact cassette) Lo strumento voce, demo Lecce 14/4/94 (magnetic tape 1/8, SONY Metal-xr 100, compact cassette) Metrodora (long play disc) Napoli (magnetic tape 1/8 BASF Chromdioxid 60, compact cassette) Nastro cantanti 75/78 (magnetic tape, BASF, plastic flange) Nastro pre-tesi, copia nastro Tesi, Stratos vocalizzi riversati (magnetic tape 1/8, BASF Chromdioxid 60, compact cassette) Nastro Tesi su Demetrio Stratos (magnetic tape 1/8, BASF Cromdioxid 90, compact cassette) Spectrograph7 (Stratos) (magnetic tape, BASF Scotch, plastic flange) Spectrograph 20 (magnetic tape, BASF, aluminium flange) Stratos Ferrara (magnetic tape 1/,BASF Chromdioxid 90, compact cassette) Stratos Milano (magnetic tape 1/8, TDK, SF60, compact cassette) Stratos suo nastro (magnetic tape 1/8, TDK KR C60, compact cassette) Slides (mixed), ISTC archive, Padua Lo strumento voce, demo Lecce 14/4/94, transparencies, ISTC archive, Padua Transparencies, no date, ISTC archive, Padua (two parcels) Abbreviation daa-cv daa-ct daa-d daa-svl daa-m daa-n daa-nc75/78 daa-npt daa-ntd daa-s7 daa-s20 daa-sf daa-sm daa-ssn dav-d dav-lsv dav-l (two parcels)

6 SOURCE Accordi M., Croatto L., Ferrero F. E., Analisi spettrografica di alcuni vocalizzi di Demetrio Stratos. In Il Valsalva, bollettino italiano di audiologia e foniatria, Vol. V N. 1, January – April 1982, pp. 2-8 Accordi M., Croatto L., Ferrero F. E., Descrizione elettroacustica di alcuni tipi di vocalizzo di Demetrio Stratos. In Rivista Italiana di Acustica, Vol. IV N , pp Accordi M., Croatto L., Ferrero F. E., Descrizione elettroacustica di alcuni tipi di vocalizzo di Demetrio Stratos. In Rivista Italiana di Acustica, Vol. IV N , pp , copy of the original typewritten publication Accordi M., Ferrero F., Ricci Maccarini A., Tisato G., Il canto difonico, un esempio delle possibilità del tratto vocale, comunicazione presentata al XVIth Congress of Union of the European Phoniatricians, Salsomaggiore, Ottobre In Quaderni del centro di studio per le ricerche di fonetica, vol. IX, 1990, pp Baroni Vittore, Cometa Rossa: la Musica è un Gioco Rischioso, pp , no date Battain Valeria, Un archivio di documenti sonori non convenzionale: il fondo Demetrio Stratos dell’istc (Istituto di Scienze e Tecnologie della Cognizione, ex Istituto di Fonetica e Dialettologia) del CNR di Padova. Thesis of the Academic year , Università degli studi di Udine, Supervisor: Professor Sergio Canazza Targon Cantare la voce, poster, congress programme and brochure, Monday 29th e Tuesday 30th May 1989, ISTC archive, Padua Copiello Laura Demetrio Stratos, una vocalità riscoperta. Thesis of the Academic year , Università degli studi di Venezia, Supervisors: Professori Giovanni Morell, Graziano Tisato e Domenico Stanzial Fariselli Loretta, Fariselli Patrizio, Demetrio Stratos Area, dieci anni di musica ed impegno, programme of the demonstration on the 4th of July at 9.00 pm in Piazza Mercato, Marghera, unpuplished work Ferrero E. Franco, Attività di studi e ricerca sulla voce cantata, study presented at Seminario CIRM, 5 Febbraio 1997, unpublished work Ferrero E. Franco, Caratteristiche elettroacustiche di alcune singolari vocalizzazioni di Stratos Demetriou, Centre for the study of phonetic researches (CNR) in Padua, unpublished work Ferrero E. Franco, Elenco delle pubblicazioni, 30 Settembre 1997, ISTC archive, Padua Ferrero F., Ricci Maccarini A., Tisato G., I suoni multifonici nella voce umana, article presented at XIX Convegno Nazionale Aprile 1991, Napoli, pp Ferrero Franco, Elementi di Fonetica, publication n. 85 from the list of publications, pp Ferrero Franco (hypothesis of the autor based on the hand writing), Fonetografia e costo vocale, study, without date, ISTC archive, Padua, unpublished work Ferrero Franco, La fonetica strumentale in funzione della diagnostica foniatrica e della riabilitazione logopedica, notepad bound by hand, handwriting by Ferrero, without date, ISTC archive, Padua Ferrero Franco, Lo strumento voce, study, without date, ISTC archive, Padua Ferrero Franco, three lists of thesis (supervisor F. Ferrero), ordered by location, Academic year and alphabetical order of the titles, without date, ISTC archive, Padua Tissue paper sheets, without date, ISTC archive, Padua Sheet of paper with the description of vocalizes 18 and 6 (copy of a page Caratteristiche elettroacustiche di alcune singolari Abbreviation dav-l1 (first parcel) dav-l2 (second parcel) dc-val82 dc-riv80 dc-riv80/cp dc-cdif dc-com dc-t/batt dc-cv/l (poster) dc-cv/p (congress programme) dc-cv/o (brochure) dc-t/cop dc-far/09 dc-cirm dc-ce/cnr dc-ep dc-sm dc-ef dc-fon dc-fs/lib dc-sv dc-t/el dc-fcv dc-l1 SOURCE vocalizzazioni di Stratos Demetriou attached to the first parcel of transparencies), without date, ISTC archive, Padua Fortunato Roberto, Rinasce la ricercata etichetta Cramps. In Il mattino, Tuesday 11th July 1989, pp. 41 Gatti Roberto, In alto la voce. In L’Espresso, 4th of June 1989, pp Kemp Alan, Linsdey Geoff, Verhoeven Jo, Practical Phonetics, Edinburgh University Linguistics Department, pp. 1-8, without date La musique religieuse du Thibet, Bulletin du Groupe d’acoustique Musicale, 58, Université Paris VI, 1972 Lo strumento voce, demo Lecce 14/4/94, sheets with notes Transparencies, paper copy, without date, ISTC archive, Padua, (two parcels) Mangiarotti Marco, Stratos: la musica è gioia e rivoluzione. In Il giorno, Sunday 25th June 1989 Mattarelli Luca, Demetrio Stratos, una nuova vocalità. Thesis of the Academic year , Università degli studi di Bologna, Supervisor: Professor Gino Stefani Nastro cantanti 75/78, cover with notes, without date, ISTC archive, Padua Ricci Maccarini Andrea, Il canto difonico. Thesis of the Academic Year , Università degli studi di Padova, Supervisor: Professor Maurizio Accordi, Co-Relatore: Dott. Franco Emilio Ferrero Receipt of payment to Franco Ferrero for the conference he held on the 29th of September in the auditorium San Rocco Vocal Music Festival called Caratteristiche elettroacustiche di alcuni tipi di vocalizzo di Demetrio Stratos Sonagrams (mix), ISTC archive, Padua Spectrograph 7 (Stratos), white cardboard with notes and writings, without date, ISTC archive, Padua Spectrograph 20, sheet with notes, without date, ISTC archive, Padua Vocalizzi di Stratos (pre-tesi), sheet with notes, without date, ISTC archive, Padua Vocalizzi Tesi, sheet with notes, without date, ISTC archive, Padua Zecchin Franca, Studio elettroacustico di alcuni vocalizzi di Demetrio Stratos. Thesis of the Academic Year , Università degli studi di Padova, Supervisor: Professor Franco Ferrero Copia disco dimostrazione Titze, conservative copy CIF0001 of the ISTC archive (DVD-data: 2+2 tracks, WAV, 96kHz- 24bit) Demetrio, conservative copy CIF0002 of the ISTC archive (DVD-data: 2 tracks, WAV, 96kHz-24bit) Nastro cantanti 75/78, conservative copy CIF0008_CCIR of the ISTC archive (DVD-data: 2 tracks, WAV, 96Hz-24bit) Nastro cantanti 75/78, conservative copy CIF0008_NAB of the ISTC archive (DVD-dati: 2 tracks, WAV, 96Hz-24bit) Nastro cantanti 75/78, conservative copy CIF0008_V of the ISTC archive (DVD- data: 1 track, MOV) Nastro tesi su Demetrio Stratos, conservative copy CIF0006 of the ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Spectrograph7 (Stratos), conservative copy CIF0007 of the ISTC archive (DVD- data: 1 track, WAV, 96kHz-24bit) Spectrograph7 (Stratos), conservative copy CIF0007_V of the ISTC archive (DVD- data: 1 track, MOV) Spectrograph 20, conservative copy CIF0009_CCIR of the ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Abbreviation dc- R.CRAMPS/M at dc-iav/esp dc-pp dc-mr/th dc-sv/app dc-lc (two parcels) dc-l1 (first parcel) dc-l2 (second parcel) dc-mgr/gio dc-t/matt dc-nc75/78 dc-t/ric dc-ric DC-SON DC-SP7 dc-sp20 dc-voc/pt dc-voc/t dc-t/zecc DDA-1 DDA-2 DDA-8/C DDA-8/N DDA-8/V DDA-6 DDA-7 dda-7/v DDA-9/C Spectrograph 20, conservative copy CIF0009_NAB of the DDA-9/N

7 SOURCE ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Spectrograph 20, conservative copy CIF0009_V of the ISTC archive (DVD- data: 1 track, MOV) Stratos Ferrara, conservative copy CIF0004 of the ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Stratos Milano, conservative copy CIF0003 of the ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Stratos suo nastro, conservative copy CIF0005 of the ISTC archive (DVD- data: 2 tracks, WAV, 96kHz-24bit) Abbreviation DDA-9/V DDA-4 DDA-3 DDA-5 Table 2. Sources for the study of Demetrio Stratos at the ITSC. Several additional sources are not listed here: these are articles, dissertations, projection papers, sleeves/sheets and annotations related to the audio material. The existence of documentations scattered over an extended period of time from the Seventies up to now tells not only the interest towards Stratos, it also ensure the importance of his musical research. 4.3Conservation and Preservation This project ultimate aim has been to preserve the entire documentation from obsolescence and deterioration; that is why, following the typology of sources, a digital archive has been made, which is now available at the ISTC. The digital archive purpose is: 1) to preserve a specific order (folders e.g. digitization of paper materials are maintained in the same sequence of the original sources), so that the sources cannot get lost in different places; 2) to preserve the chronology of their creation; 3) to guarantee the accessibility to whoever is interested; 4) to avoid damages to the authentic sources that could be caused by an incorrect use. The archive refines and benefits of a previous research. In 2007 Valeria Battain created digital conservative copies of the entire documentation related to Demetrio Stratos at the ISTC [15]. The storage in digital format included three magnetic open tape reels (daa-nc75/78, daa-s7, daa-s20) and six compact cassettes (daa-ct, daa- D, daa-ntd, daa-sf, daa-sm, daa-ssn). Battain s study provides a descriptive paper and picture for each original source; it also includes other papers with technical information related to the process. It was however incomplete. The new digital archive is divided into two parts: the first one is labeled ARCHIVIO Demetrio Stratos, ISTC (Istituto di Scienze e Tecnologie della Cognizione), CNR, Padova ; it relates to a selected space inside one of the shelves at the ISTC; it correspond to tangible documents (e.g. thesis, tapes, compact-cassettes, DVD with recordings made by the eng. Sergio Canazza, etc.); the second part is an external HD USB with the whole sources that have been digitized during this work. For the moment, the archive can be accessed only locally through the computers of the Institute (ISTC). The structure of the archive reflects the choice made in organizing the whole sources. It simply systematizes them in 4 macrocategories: analogue audio document (daa), visual analogue document (dav), paper document (dc), audiovisual digital document (dda). Each folder is a container for the digitalized documents. These are: 14 analogue audio documents, 14 audiovisual documents (digital), 4 visual documents ( analogue ), 40 paper documents. The documents are identifiable through the abbreviated text extension given during this research, instead of verbose and long names (see Table 2). 5. CONCLUSIONS The reconstruction of Stratos experience in Padova has been made possible by the collection, the description, the analysis and the comparison of sources. Yet, this study is needless to say the first step toward investigating Stratos contribute to XX century vocal research. Just as an example, Stratos position in the avant-garde vocal research is almost completely unknown, but many aspects of his life are critical. Area member Paolo Tofani recalls the precise moment when Stratos realized the novelty of the overtone singing [19]. It was in 1976/77, when a journalist brought to the group an audiocassette with sounds sung by Mongolians: Demetrio tried and tried until he finally succeeded, because he had been influenced by John Cage; they also went to meet Cathy Berberian repeatedly and took lessons from Tran Quang Hai [19]. Also, his friendship with Nicola Bernardini, member of Prima Materia Group, is crucial. And needless to say, the milieu and historical period in which Stratos research took place are again crucial: the Seventies, when the youth movement reached Italy and the children of the second world war began their protest against the established culture and lifestyle. It is easy to state that this social rebellion reflects in the complete nonconformity and subversion of Stratos technique, an aspect that affected Stratos position in the musical industry, since his voice did not respect standardized vocal production, did not consider language s rules and, on the contrary, tried to get loose from the detention of the communicative act. Future studies need to take into account all aspects of this issue. The investigation of Stratos vocal effects may develop in two directions. The first one is related to the systematic investigation of the complete series of Stratos vocalizes, which had not been analyzed so far (as said in 3.4). The second one could help in deducing Stratos phonatory attitude: Voice Quality (VQ) methodologies and glottal source modelization techniques should be applied to the existing glottal tracks. In addition to the traditional parameters (Shimmer, i.e. the amplitude perturbations of the wave form; Jitter, i.e. the pitch perturbations; the Waveform Matching Coefficient, i.e. the cross-correlation between near periods; the Harmonics-to-Noise Ratio, i.e. the energy ratio between the harmonic partials and the noise components; etc.), it is in fact possible to extract more meaningful information: for example, the Glottal to Noise Excitation Ratio (GNE), which is used to discriminate among normal and pathological voices [20]. The available glottic tracks could give precious information about the glottal flow, in term of Open Quotient Oq = Te / T0, i.e. the ratio between the maximum excitation instant Te and the sound period T0, and the Return phase quotient Qa, the ratio between the return phase (in which the glottal flow reaches zero) and the closed phase of the vocal folds. The Return phase quotient proved to be the

8 most effective index of VQ, for it determines the sound Spectral tilt, i.e. the slope of the frequency envelope [21]. Another development is the one mentioned before. A web page of the archive would also be desirable (possibly at: with the audio vocal material and the PDF documents (of course in agreement with the authors). Accessing the stock of documents via metadata would be imperative. The web access would guarantee a more large accessibility to the sources; this also should adhere to Stratos personal interest in the study and dissemination of his own personal research. Acknowledgments We would like to thank Piero Cosi, Alberto Benin, Nicola Bernardini, Ferdinando Bersani, Maurizio Accordi, Oskar Schindler, Francesco Avanzini, Area members Paolo Tofani, Ares Tavolazzi, Patrizio Fariselli and Claudio Rocchi, Valeria Battain, Kyriaki Vagges and Franca Zecchin, Sergio Canazza Targon and Daniela Ronconi Demetriou. This research would not have been possible without their help and advice. 6. REFERENCES [1] J. El Haouli (1999), Demetrio Stratos, alla ricerca della voce-musica, Milano, Casanova e Chianura edizioni, 1999/2009. [2] N. Bernardini, A. Vidolin, Sustainable live electro-acoustic music, Cdrom proceedings Sound and Music Computing 2005 XV, CIM – Nov , Salerno, Italy, [3] L. Zattra, Studiare la computer music. Definizioni, analisi, fonti, (collana biblioteca contemporanea), libreriauniversitaria.it, 2011, ISBN [4] L. Zattra Sources and philological problems in the study of Computer Music, in Elektroakustische Musik: Technologie, Aesthetik und Theorie als Herausforderung an die Musikwissenschaft, T. Boehme-Mehner, K. Mehner, M. Wolf eds., Essen, Die Blaue Eule Verlag, 2008, pp [5] E. Ceolin, Demetrio Stratos a Padova: la storia, le fonti, l archivio, Graduation Thesis, DAMS, Supervisor: S. Durante, L. Zattra, March [6] D. Ronconi Demetriou, interview given to Elena Ceolin, June 25, [7] M. Accordi, interview given to Elena Ceolin, October 5, [8] K. Vagges, interview given to Elena Ceolin, February 18, [9] F. Zecchin, Studio elettroacustico di alcuni vocalizzi di Demetrio Stratos, graduation thesis, , Università degli studi Padova, Supervisor: Prof. Franco Ferrero, [10] G. Tisato, interview given to Elena Ceolin, February 7, [11] F. Zecchin, interview given to Elena Ceolin, February 17, [12] M. Accordi, L. Croatto, F. Ferrero, Descrizione elettroacustica di alcuni tipi di vocalizzo di Demetrio Stratos, in «Rivista Italiana di Acustica», Vol. IV N. 3, 1980, pp [13] M. Caraci Vela, La filologia musicale. Istituzioni, storia, strumenti critici, Vol. 1, LIM, [14] F. Ferrero, A. Ricci Maccarini, G. Tisato (1991), I suoni multifonici nella voce umana, in XIX Convegno Nazionale AIA Aprile 1991, Napoli, 1991, pp [15] L. Battain (2007), Un archivio di documenti sonori non convenzionale: il fondo Demetrio Stratos dell’istc (Istituto di Scienze e Tecnologie della Cognizione, ex Istituto di Fonetica e Dialettologia) del CNR di Padova, Graduation Thesis , Università degli studi di Udine, Supervisor: Prof. Sergio Canazza Targon, [16] L. Copiello, Demetrio Stratos, una vocalità riscoperta. Graduation Thesis , Università degli studi di Venezia, supervisors: Proff.s G. Morelli, G. Tisato e D. Stanzial, [17] N. Bernardini, interview given to Elena Ceolin, June 8, [18] G. Tisato, Analisi e sintesi del Canto Difonico, in Proceedings VII Colloquio di Informatica Musicale (CIM), Cagliari, 1989, pp [19] P. Tofani, interview given to Elena Ceolin, March 21, 2011 (in the presence of G. Tisato and Giovanni Floreani). [20] D. Michaelis, M. Froehlich, H.W. Strube, Selection and combination of acoustic features for the description of pathologic voices in J. of the Acoust. Soc. Am., 103(3), 1998, pp [21] B. Doval, C. d’alessandro, N. Henrich, The spectrum of glottal flow models in Acta Acustica, 92, 2006, pp , age_2


Laura Zattra (Musicologist) obtained her PhD (2003) in Music and Musicology at the Sorbonne Paris IV under the direction of Marc Battier and in Musical Sciences at Trento University under the direction of Rossana Dalmonte. She pursued post-doctoral studies at the University of Padova, she obtained research grants from the same university (2006-2012), from EHESS Lyon (2002-3), De Monfort University (2008-9), Calgary University (2011), from CNRS France (2012) and IRCAM in Paris (2017). Her writings include the book Studiare la computer music. Definizioni, analisi, fonti (2011), Musica e famiglia. L’avventura artistica di Renata Zatti (2010), Invenzione Musicale (L.Zattra ed., 2012), the co-edition of Presenza storica di Luigi Nono (2011) and Vent’anni di musica elettronica all’università di Padova (2002) as well as articles and book chapters (Computer Music Journal, Contemporary Music Review, Musicae Scientiae, Journal of New Music Research, Organised Sound, Musimédiane…; she recently curated two entries for the Italian Encyclopedia Treccani). She is a member of the Associazione di Informatica Musicale Italiana, the APM équipe at IRCAM Paris, the IReMus at Sorbonne Paris IV, the Electroacoustic Music Studies Network. Her musicological expertise covers the twentieth century and particularly of the post-World War II period and XXI century, the analysis of electroacoustic music, the philology of music, the interaction of music and technology, ethnography and oral history applied, women composers, the analysis of compositional process.

Graziano Tisato :


Intervista a Graziano Tisato, ricercatore CNR Padova

“Il canto difonico” ne parliamo con Graziano Tisato, ricercatore CNR Padova

Graziano Tisato

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Posted on January 6, 2015 by haidiphonie

Piero Cosi, Graziano Tisato
Istituto di Scienze e Tecnologie della Cognizione – Sezione di Fonetica e Dialettologia
(ex Istituto di Fonetica e Dialettologia) – Consiglio Nazionale delle Ricerche
e-mail: cosi@csrf.pd.cnr.it tisato@tin.it
www: http://nts.csrf.pd.cnr.it/Ifd
I really like to remember that Franco was the first person I met when I approached the “Centro di Studio per le Ricerche di Fonetica” and I still have a greatly pleasant and happy sensation of that our first warm and unexpectedly informal talk. It is quite obvious and it seems rhetorical to say that I will never forget a man like Franco, but it is true, and that is, a part from his quite relevant scientific work, mostly for his great heart and sincere friendship.
For “special people” scientific interests sometimes co-occur with personal “hobbies”. I remember Franco talking to me about the “magic atmosphere” raised by the voice of Demetrio Stratos, David Hykes or Tuvan Khomei1 singers and I still have clear in my mind Franco’s attitude towards these “strange harmonic sounds”. It was more than a hobby but it was also more than a scientific interest. I have to admit that Franco inspired my “almost hidden”, a part from few very close “desperate” family members, training in Overtone Singing2. This overview about this wonderful musical art, without the aim to be a complete scientific work, would like to be a small descriptive contribute to honor and remember Franco’s wonderful friendship.
“Khomei” or “Throat-Singing” is the name used in Tuva and Mongolia to describe a large family of singing styles and techniques, in which a single vocalist simultaneously produces two (or more) distinct tones. The lower one is the usual fundamental tone of the voice and sounds as a sustained drone or a Scottish bagpipe sound. The second corresponds to one of the harmonic partials and is like a resonating whistle in a high, or very high, register. For convenience we will call it “diphonic” sound and “diphonia” this kind of phenomenon.
Throat-Singing has almost entirely been an unknown form of art until rumours about Tuva and the peculiar Tuvan musical culture spread in the West, especially in North
1 We transcribe in the simplest way the Tuvan term, for the lack of agreement between the different authors: Khomei, Khöömii, Ho-Mi, Hö-Mi, Chöömej, Chöömij, Xöömij.
2 This is the term used in the musical contest to indicate the diphonic vocal techniques.
America, thanks to Richard Feynman [1]3, a distinguished American physicist, who was an ardent devotee of Tuvan matters.
This singing tradition is mostly practiced in the Central Asia regions including Bashkortostan or Bashkiria (near Ural mountains), Kazakhstan, Uzbekistan, Altai and Tuva (two autonomous republics of the Russian Federation), Khakassia and Mongolia (Fig. 1), but we can find examples worldwide: in South Africa between Xosa women [3], in the Tibetan Buddhist chants and in Rajastan.
The Tuvan people developed numerous different styles. The most important are: Kargyraa (chant with very low fundamentals), Khomei (it is the name generally used to indicate the Throat-Singing and also a particular type of singing), Borbangnadyr (similar to Kargyraa, with higher fundamentals), Ezengileer (recognizable by the quick rhythmical shifts between the diphonic harmonics), Sygyt (like a whistle, with a weak fundamental) [4]. According to Tuvan tradition, all things have a soul or are inhabited by spiritual entities. The legends narrate that Tuvan learnt to sing Khomei to establish a contact and assimilate their power trough the imitation of natural sounds. Tuvan people believe in fact that the sound is the way preferred by the spirits of nature to reveal themselves and to communicate with the other living beings.

Figure 1. Diffusion of the Throat-Singing in Central Asia regions.
In Mongolia most Throat-Singing styles take the name from the part of the body where they suppose to feel the vibratory resonance: Xamryn Xöömi (nasal Xöömi), Bagalzuuryn Xöömi (throat Xöömi), Tseedznii Xöömi (chest Xöömi), Kevliin Xöömi (ventral Xöömi, see Fig. 13), Xarkiraa Xöömi (similar to the Tuvan Kargyraa), Isgerex (rarely used style: it sounds like a flute). It happens that the singers itself confuse the different styles [5]. Some very famous Mongol artists (Sundui and Ganbold, for example) use a deep vibrato, which is not traditional, may be to imitate the Western singers (Fig. 13).
The Khakash people practice three types of Throat-Singing (Kargirar, Kuveder or Kilenge and Sigirtip), equivalent to the Tuvan styles Kargyraa, Ezengileer and Sygyt. We
3 Today, partly because of Feynman’s influence, there exists a society called “Friends of Tuva” in California, which circulates news about Tuva in the West [2].
find again the same styles in the peoples of the Altai Mountains with the names of Karkira, Kiomioi and Sibiski. The Bashkiria musical tradition uses the Throat-Singing (called Uzlau, similar to the Tuvan Ezengileer) to accompany the epic chants. In Uzbekistan, Kazakhstan and Karakalpakstan we find forms of oral poetry with diphonic harmonics [6].
The Tibetan Gyuto monks have also a tradition of diphonic chant, related to the religious believes of the vibratory reality of the universe. They chant in a very low register in a way that resembles (see later the difference) the Tuvan Kargyraa method. The aim of this tradition is mystical and consists in isolating the 5th or the 10th harmonic partial of the vocal sound. They produce in this way the intervals of 3rd or 5th (in relation to the fundamental) that have a symbolic relation with the fire and water elements (Fig. 14) [4].

Figure 2. Spectral section of a vocal (up) and a diphonic vocal (down).
What is so wonderful in Throat-Singing? It is the appearance of one of the harmonic partials that discloses the secret musical nature of each sound. When in Throat-Singing the voice splits in two different sounds, we experience the unusual sensation of a pure, discarnate, sine wave emerging from the sound. It is the same astonishment we feel when we see a rainbow, emerging from the white light, or a laser beam for the first time.
The natural sounds have a complex structure of harmonic or inharmonic sinusoidal partials, called “overtones” (Fig. 2). These overtones are not heard as distinct sounds, but their relative intensity defines our perception of all the parameters of sound (intensity, pitch, timbre, duration). The pitch corresponds to the common frequency distance between
the partials and the timbre takes into account all the partials as a whole. The temporal evolution of these components is what makes the sound of each voice or instrument unique and identifiable.
In the harmonic sounds, as the voice, the components are at the same frequency distance: their frequency is a multiple of the fundamental tone (Fig. 2). If the fundamental frequency is 100 Hz, the 2nd harmonic frequency is 200 Hz; the 3rd harmonic frequency is 300 Hz, and so on. The harmonic partials of a sound form a natural musical scale of unequal temperament, as whose in use during the Renaissance [7]. If we only take into consideration the harmonics that are easy to produce (and to perceive also), i.e. from the 5th to the 13th, and if we assume for convenience a C3 131 Hz as starting pitch, we can get the following musical notes:
Harm. N. Freq. (Hz) Note Interval with C3
5 655 E5 3rd
6 786 G5 5th
7 917 A+ 6th +
8 1048 C6 Octave
9 1179 D6 2nd
10 1310 E6 3rd
11 1441 F6+ 4th +
12 1572 G6 5th
13 1703 A6- 6th-
The series of 8th, 9th, 10th, 12th, 13th harmonic and the series from 6th to 10th are two possible pentatonic scales to play. Note that the frequency differences between these scales and the tempered scale are on the order of 1/8th of a tone (about 1.5%).
The Throat-Singing allows extracting the notes of a natural melody from the body of the sound itself.
The spectral envelope of the overtones is essential for the language comprehension. The glottal sound is filtered by the action of the vocal tract articulation, shaping the partials in the voice with some characteristic zones of resonance (called formants), where the components are intensified, and zones of anti-resonance, where the partials are attenuated (Fig. 2-3). So, the overtones allow us to tell apart the different vocal sounds. For example the sounds /a/, /e/, /i/, /o/, etc. uttered or sung at the same pitch, nevertheless sound different to our ears for the different energy distribution of the formants (Fig. 2).
The auditory mechanisms “fuse” the partials in one single “image”, which we identify as voice, musical instrument, noise, etc. [8]. In the same way, the processing of visual data tends to group different dots into simple shapes (circle, triangle, square, etc.). The creation of auditory images is functional to single out and to give a meaning to the sonic sources around us.
The hearing mechanisms organize the stream of perceptive data belonging to different components of different sounds, according to psychoacoustics and Gestalt principles. The “grouping by harmonicity”, for example, allows the fusion in the same sound of the frequency partials, which are multiples of a common fundamental. The “common fate” principle tells that we integrate the components of a complex sound, which show the same amplitude and frequency behaviour (i.e. similar modulation and microvariation, similar attack and decay, similar vibrato, etc.) [8]. If one of these partials reveals a particular evolution (i.e. it is mistuned or has not the same frequency and amplitude modulation, etc.),
it will be heard as a separate sound. So the Throat-Singing is a marvelous example to understand the illusory nature of perception and the musical structure of the sound.

Figure 3. Resonance envelope for an uniform vocal tract (left). A constriction on the pharynx moves the formants so that the intensity of partials in the 2500-3500 Hz region increases (right).
In the Throat-Singing the singer learn to articulate the vocal tract so that one of the formants (usually the first or the second) coincide with the desired harmonic, giving it a considerable amplitude increase (even more than 30 dB, see in Fig. 2 the 10th harmonic) and making it perceptible. Unlike the normal speech, the diphonic harmonic can exceed a lot the lower partials intensity (Fig. 2). Soprano singers use similar skill to control the position of the 1st formant, tuning it to the fundamental with the proper articulation (i.e. proper opening of the mouth), when they want to sing a high note [9].
There are many different methods to produce the diphonic sound [5-6], but we can summarize them in two possible categories, called “single cavity method” or “two cavities method”, that are characterized by the use or not of the tongue, according to the proposal of Tran Quang Hai [4].
In this method, the tongue doesn’t move and remains flat or slightly curved without touching the palate. In this case the vocal tract is like a continuous tube (Fig. 3). The selection of the diphonic harmonic is obtained by the appropriate opening of the mouth and the lips. The result is that the formants frequency raises if the vocal tract lengthens (for example with a /i/) and that the formants frequency lowers, if it extends (for example with a /u/). With this technique the 1st formant movement allows the selection of the partials. As we can see in Fig. 4, we cannot go beyond 1200 Hz. The diphonic harmonic is generally feeble, masked by the fundamental and the lower partials, so the singers nasalize the sound to reduce their intensity [10-11].

Figure 4. Opening the mouth controls the 1st formant position. The movement of the tongue affects the 2nd formant and allows the harmonic selection in a large frequency range.
In this method, the tongue is raised so to divide the vocal tract in two main resonators, each one tuned on a particular resonance. By an appropriate control, we can obtain to tune two separate harmonics, and thereby to make perceptible, not one but two (or more) pitches at the same time (Fig. 9-12).
There are three possible variants of this technique:
The first corresponds to the Khomei style: to select the desired harmonic the tip of the tongue and the tongue body moves forward (higher pitch) and backward (lower pitch) along the palate.
The second is characteristic of the Sygyt style: the tip of the tongue remains fixed behind the upper teeth while the tongue body rises to select the harmonics.
In the third variant, the movement of the tongue root selects the diphonic harmonic. Shifting the base of the tongue near the posterior wall of the throat, we obtain the lower harmonics. On the contrary, moving the base of the tongue forward, we pull out the higher harmonics [6].
A different method has been proposed by Tran Quang Hai to produce very high diphonic harmonics (but not to control the selection of the desired component). It consists
to keep the tongue pressed by the molars, while singing the vowels /u/ and /i/, and maintaining a strong contraction of the muscles at the abdomen and the throat [4].
The advantage of the two cavities techniques is that we can use the 2nd formant to reinforce the harmonics that are in the zone of best audibility. In this case the diphonic harmonic reaches the 2600 Hz (Fig. 4). Furthermore the movement of the tongue affects the formants displacement in opposite directions. The separation of the 1st and the 2nd formant produces in between a strong anti-resonance (Fig. 2), which helps the perception of the diphonic harmonic.
In all these methods it is useful a slight discrete movement of the lips to adjust the formants position.
There are three main mechanisms required to reinforce the effect of segregation of the diphonic sound:
• The appropriate movement of the lips, tongue, jaw, soft palate, throat, to produce a fluctuation in the amplitude of the selected harmonic, so that it differentiates from the other partials that remain static. The auditory mechanisms are tuned to capture the more subtle changes in the stream of auditory information, useful to discriminate the different sounds [8].
• The nasalization of the sound. In this way we create an anti-resonance at low frequency (<400 Hz) that attenuates the lower partials responsible for the masking of the higher components [10-11]. The nasalization provokes also the attenuation of the third formant [12], which improves the perception of the diphonic harmonic (Fig. 2).
• The constriction of the pharynx region (false ventricular folds, arytenoids, root of the epiglottis), which increases the amplitude of the overtones in the 2000-4000 Hz region (Fig. 2). This is also what happens in the “singer’s formant”, the technique used by the singers to reinforce the partials in the zone of best audibility and to avoid the masking of the voice by the orchestra, generally very strong in the low frequency range [9]. For this reason the Throat-Singing technique requires a tuning extremely precise and selective, in order to avoid the amplification of a group of harmonic partials, as in the “singer’s formant”.
We disregard in this paper the polyphonic singing that could produces some diphonic effects: for example the phenomenon of the quintina in the Sardinia religious singing, where the coincidence of the harmonics of 4 real voices produces the perception of a 5th virtual voice (Fig. 5) [13].
There are in the literature many terms to indicate the presence of different perceptible sounds in a single voice: Khomei, Throat-Singing, Overtone Singing, Diphonic Singing, Biphonic Singing, Overtoning, Harmonic Singing, Formantic Singing, Chant, Harmonic Chant, Multiphonic Singing, bitonality, diplophonia, vocal fry, etc.
According to the pioneer work in the domain of the vocal sounds made by The Extended Vocal Techniques Ensemble (EVTE) of San Diego University and bearing in mind that there is little agreement regarding classifications [4], [14-15], the best distinctive criterion for the diphonia seems to be the characterization of the sound sources that produce the perception of the diphonic or multiphonic sound [16].
Following this principle, we can distinguish between Bitonality and Diphonia:
• Bitonality: In this case there are two distinct sound sources that produce two sounds. The pitches of the two sounds could be or not in harmonic relationship. This category includes: diplophonia, bitonality and vocal fry.
• Diphonia: The reinforcement of one (or more) harmonic partial(s) produces the splitting of the voice in two (or more) sounds. This category includes: Khomei, Throat-Singing, Overtone Singing, Diphonic Singing, Biphonic Singing, Overtoning, Harmonic Singing, Chant, Harmonic Chant.

TISATO 5 FIG 5 - Copie
Fig. 5 Sardinia religious folk singing. The pitches of the 4 voices of the choir are F1 88 Hz, C2 131 Hz, F2 176 Hz, A3# 230 Hz. The 8th harmonic of the F1, the 6th of the C2, the 4th of the F2 and the 3rd of the A# coincide at 700 Hz and produce the perception of a 5th voice.
Diplophonia: The vibration of the vocal folds is asymmetrical. It happens that after a normal oscillatory period, the vibration amplitude that follows is reduced. There is not the splitting of the voice in two sounds, but the pitch goes down one octave lower and the timbre assumes a typical roughness. For example, assuming as fundamental pitch a C3 130.8 Hz, the resulting pitch will be C2 65.4 Hz. If the amplitude reduction happens after two regular vibrations, the actual periodicity triplicates and then the pitch lowers one octave and a 5th. The diplophonic voice is a frequent pathology of the larynx (as in unilateral vocal cord paralysis), but can be also obtained willingly for artistic effects (Demetrio Stratos was an expert of this technique) [16-18].
Bitonality: The two sound sources are due to the vibration of two different parts of the glottis cleft. This technique requires a strong laryngeal tension [16-17]. In this case there is not necessarily a harmonic relationship between the fundamentals of the two sounds. In the Tuvan Kargyraa style, the second sound source is due to the vibration of the supraglottal structures (false folds, arytenoids, aryepiglottic folds that connects the arytenoids and the epiglottis, and the epiglottis root). In this case generally (but not always) there is a 2:1 frequency ratio between the supraglottal closure and vocal folds closure. As in the case of Diplophonia, the pitch goes down one octave lower (or more) [19-21].
Vocal fry: The second sound is due in this case to the periodic repetition of a glottal pulsation of different frequency [14]. It sounds like the opening of a creaky door (another common designation is “creaky voice”). The pulse rate of vocal fry can be controlled to produce a range from very slow single clicks to a stream of clicks so rapid to be perceived as a discrete pitch. Therefore vocal fry is a special case of bitonality: the perception of a second sound depends on a pulses train rate and not on the spectral composition of the single sound.
Diphonic and Biphonic refer to any singing that sounds like two (or more) simultaneous pitches, regardless of technique. Use of these terms is largely limited to academic sources. In the scientific literature the preferred term to indicated Throat-Singing is Diphonic Singing.
Multiphonic Singing indicates a complex cluster of non-harmonically related pitches that sounds like the vocal fry or the creaky voice [14]. The cluster may be produced expiring as normal, or also inhaling the airflow.
Throat Singing is any technique that includes the manipulation of the throat to produce a melody with the harmonics. Generally, this involves applying tension to the region surrounding the vocal cords and the manipulation of the various cavities of the throat, including the ventricular folds, the arytenoids, and the pharynx.
Chant generally refers to religious singing in different traditions (Gregorian, Buddhist, Hindu chant, etc.). As regards the diphonia, it is noteworthy to mention the low singing practiced by Tibetan Buddhist monks of the Gyuto sect. As explained before, they reinforce the 5th or the 10th harmonic partial of the vocal sound for mystical and symbolic purposes (Fig. 14). This kind of real diphonia must be distinguished from resonantial effects (enhancement of some uncontrolled overtones) that we can hear in Japanese Shomyo Chant [4] and also in Gregorian Chant.
Harmonic Singing is the term introduced by David Hykes to refer to any technique that reinforces a single harmonic or harmonic cluster. The sound may or may not split into two or more notes. It is used as a synonym of Overtone Singing, Overtoning, Harmonic Chant and also Throat-Singing.
Overtone Singing can be considered to be harmonic singing with an intentional emphasis on the harmonic melody of overtones. This is the name used by Western artists that utilizes vowels, mouth shaping, and upper-throat manipulations to produce melodies and textures. It is used as a synonym of Harmonic Singing, Overtoning, Harmonic Chant and also Throat-Singing.

Fig. 6 Tuvan Khomei Style. The fundamental is a weak F#3+ 189 Hz. The diphonic harmonics are the 6th (C#6+ 1134 HZ), 7th (E6 1323 Hz), 8th (F#6+ 1512 Hz), 9th (G#6+ 1701 Hz), 10th (A#6+ 1890 Hz) and 12th (C#7+ 2268 Hz).
Although there is no widespread agreement, Khomei comprises three major basic Throat-Singing methods called Khomei, Kargyraa, and Sygyt, two main sub methods called Borbangnadyr and Ezengileer and various other sub styles.
Khomei means “throat” or “pharynx” and it is not only the generic name given to all throat-singing styles for Central Asia, as underline above, but also a particular style of singing. Khomei is the easiest technique to learn and the most practiced in the West. It produces clear and mild harmonics with a fundamental usually within the medium range of the singer’s voice (Fig. 6). In Khomei style there are two (or more) notes clearly audible. Technically the stomach remains relaxed and there is a low-level tension on larynx and ventricular folds, whereas Sygyt style requires a very strong constraint of these organs (Fig. 7). The tongue remains seated flatly between the lower teeth as in the Single Cavity technique, or raises and moves as in the Two Cavities techniques. The selection of the desired harmonic comes mainly from a combination of different lips, tongue and throat movements.
Sygyt means “whistle” and actually sounds like a flute. This style is characterized by a strong, even piercing, harmonic and can be used to perform complex and very distinct melodies (Fig. 10). It has its roots in the Khomei method and has the same range for the fundamental. Sygyt is sung with a half-open mouth and the tip of tongue placed behind front teeth as if pronouncing the letter “L”. The tongue tip is kept in the described position, while the tongue body moves to select the harmonic. This is the same technique described above for the Khomei method. The difference is in the timbre quality of the sound lacking of energy in the low frequencies. To produce a crystal-clear, flute-like overtone,
characteristic of the Sygyt style, it is necessary to learn how to filter out the lower harmonic components, that usually mask the overtone sensation.

Figure 7. Position of the arytenoids in Khomei (left) and Sygyt style [21].
Crucial for achieving this goal is a considerable pressure from the belly/diaphragm, acting as a bellows to force the air through the throat. Significant tension is required in the throat as well, to bring the arytenoids near the root of the epiglottis (Fig. 7). In this way, we obtain the displacement of first 3 formants in the high frequency zone (Fig. 3). The result is that the fundamental and the lower harmonics are so attenuated to be little audible (Fig. 10).
It is possible to sing Sygyt either directly through the center of the mouth, or, tilting the tongue, to one side or the other. Many of the best Sygyt singers “sing to the side”: directing the sound along the hard surfaces of the teeth enhances the bright, focused quality of the sound.
Kargyraa style produces an extremely low sound that resembles the roaring of a lion, the howling of a wolf, and the croaking of a frog and all these mixed together (Fig. 9). Kargyraa means “hoarse voice”. As hawking and clearing the throat before speaking Kargyraa is nothing else than a deep and continuous hawking. This hawking must rise from the deepest part of the windpipe; consequently low tones will start resonating in the chest. Overtones are amplified by varying the shape of the mouth cavity and the position of the tongue. Kargyraa is closely linked to vowel sounds: the selection of diphonic harmonic corresponds to the articulation of a particular vowel (/u/, /o/, //, /a/, etc.), which the singer learnt to associate with the desired note.
This technique is a mixture of Diphonia and Bitonality (see 6.1): in fact the supraglottal structures start to vibrate with the vocal folds, but at a half rate. The arytenoids also can vibrate touching the root of the epiglottis, hiding the vocal folds and forming a second “glottic” source [21]. The perceived pitch will be one octave lower than normal (Fig. 9), but also one octave and a 5th lower [20]. In the case of Tran Quang Hai voice, the fibroendoscopy reveals the vibration and the strong constriction of the arytenoids that hide completely the vocal folds (Fig. 8).
We must distinguish this technique from the Tibetan Buddhist chant, which is produced with the vocal folds relaxed as possible, and without any supraglottal vibration. The Tibetan chant is more like the Tuvan Borbangnadyr style with low fundamentals.

Figure 8. Simulation of the Kargyraa style by Tran Quaang Hai: the arytenoids move against the root of the epiglottis and hide the vocal folds [21].
Borbangnadyr is not really a style, as are Khomei, Sygyt and Kargyraa, but rather a combination of effects applied to one of the other styles. The name comes from the Tuvan word for “rolling”, because this style features highly acrobatic trills and warbles, reminiscent of birds, babbling brooks, etc. While the name Borbangnadyr is currently most often used to describe a warbling applied to Sygyt, it is also applied to some lower-pitched singing styles, especially in older texts. The Borbangnadyr style with low fundamentals sounds like the Tibetan Buddhist chant.
Rather the pitch movement of the melody, Borbangnadyr generally focuses the attention on three different harmonics, the 8th, 9th, and 10th, which periodically take their turn in prominence (Fig. 11). In this style the singer easily can create a triphonia effect between the fundamental, a second sound corresponding to the 3rd harmonic at an interval of 5th, and the tremolo effect on the higher harmonics.
Ezengileer comes from a word meaning “stirrup” and features rhythmic harmonic oscillations intended to mimic the sound of metal stirrups, clinking to the beat of a galloping horse (Fig. 12). Ezengileer is a variant of Sygyt style and differs considerably from singer to singer, the common element being the “horse-rhythm” of the harmonics.
In the West the Overtone Singing technique has unexpectedly become very popular, starting into musical contests and turning very soon to mystical, spiritual and also therapeutic applications. The first to make use of a diphonic vocal technique in music was Karlheinz Stockhausen in Stimmung [22]. He was followed by numerous artists and amongst them: the EVTE (Extended Vocal Techniques Ensemble) group at the San Diego University in 1972, Laneri and his Prima Materia group in 1973, Tran Quang Hai in 1975, Demetrio Stratos in 1977 [17-18], Meredith Monk in 1980, David Hykes and his Harmonic Choir in 1983 [23], Joan La Barbara in 1985, Michael Vetter in 1985, Christian Bollmann in 1985, Noah Pikes in 1985, Michael Reimann in 1986, Tamia in 1987, Bodjo Pinek in 1987, Josephine Truman in 1987, Quatuor Nomad in 1989, Iegor Reznikoff in 1989, Valentin Clastrier in 1990, Rollin Rachele in 1990 [24], Thomas Clements in 1990, Sarah Hopkins in 1990, Les Voix Diphoniques in 1997.

Figure 9. Vasili Chazir sings “Artii-sayir” in the Kargyraa Tuvan style. The fundamental pitch is B1 61.2 Hz. The diphonic harmonics are the 6th (F#4- 367 HZ), 8th (B4 490 Hz), 9th (C#5 550 Hz), 10th (D#5- 612 Hz) and 12th (F#5- 734 Hz). The diphonic (but not perceptible) harmonics 12th-24th are in octave with the previous one. In the 2600-2700 Hz region, a steady formant amplifies the 43rd and 44th harmonics.

Figure 10. Tuvan Sygyt style. The fundamental is a weak E3+ 167 Hz. The melody uses the 8th (E6+ 1336 Hz), 9th (F#6+ 1503 Hz), 10th (G#6+ 1670 Hz) and 12th (B6+ 2004 Hz). There is a rhythmic shift between contiguous harmonics each 900 ms. In the 3000-3200 Hz zone, we can see a second resonance region.

TISATO 11 FIG 11.jpg
Figure 11. Tuvan Borbangnadyr style. The fundamental is a weak F#2 92 Hz. We can see on the harmonics 7-11 the effect of a periodic formantic shift (6 Hz about).

Figure 12. Tuvan Ezengileer style. The fundamental is A#2 117 Hz.
The most famous proponent of this type of singing is David Hykes. Hykes experimented with numerous innovations including changing the fundamental (moveable drone) and keeping fixed the diphonic formant, introducing text, glissando effects, etc., in numerous works produced with the Harmonic Choir of New York (Fig. 15) [23].
In the recent past, some work has been done on the analysis of Khomei, and more has been done on Overtone Singing generally. The focus on this research has been on the effort to discover exactly how overtone melodies are produced. Hypotheses as to the mechanics of Overtone Singing range from ideas as to the necessary physical stance and posture used by the singer during a performance, to the actual physical formation of the mouth cavity in producing the overtones.
Aksenov was the first to explain the diphonia as the result of the filtering action of the vocal tract [25-27]. Some years later Smith et al. engaged in an acoustical analysis of the Tibetan Chant [28]. In 1971, Leipp published an interesting report on Khomei [29]. Tran Quang Hai carried out a deep research on all the diphonic techniques [4-5][30]. The mechanism of the diphonia was demonstrated in 1989 by two different methodologies. The first applied direct clinical-instrumental methods to study the vocal tract and vocal cords [31-32]. The optic stroboscope revealed the perfect regularity of the vocal folds vibration. The second method made use of a simple linear prediction model (LPC) to analyse and synthesize the diphonic sound [33-34]. The good quality of the resynthesis demonstrated that the diphonia is due exclusively to the spectral resonance envelope. The only difference between normal and diphonic sound consists in the unusual narrow bandwidth of the prominent formant.
Several researchers seem to agree that the production of the harmonics in Throat-Singing is essentially the same as the production of an ordinary vowel. Bloothooft reports an entire investigation of Overtone Singing, based on the similarity of this kind of phonation to the articulation of vowel [10].
Other authors, on the contrary, argue that the physical act of creating overtones may originate in vowel production, but the end product, the actual overtones themselves, are far from vowel-like [35]. They stated, in fact, that for both acoustic and perceptual reasons, the production of an overtone melody cannot be described as vowel production.
Acoustically, a vowel is distinctive because of its formant structure. In Overtone Singing, the diphonic formant is reduced to one or a few harmonics, often with surrounding harmonics attenuated as much as possible. Perceptually, Overtone Singing usually sounds nothing like an identifiable vowel. This is primarily because, a major part of the overtone-sung tone has switched from contributing to the timbre of the tone to provoking the sensation of melody and such a distorted “vowel” can convey little phonetic information.
All musical sounds contain overtones or tones that resonate in fixed relationships above a fundamental frequency. These overtones create tone color, and help us to differentiate the sounds of different music instruments or one voice and another.
Different cultures have unique manifestations of musical traditions, but, what it is quite interesting, is that some of them share at least one aspect in common: the production of overtones in their respective vocal music styles. Among these, each tradition has also its own meanings and resultants from Overtone Singing, but they are often related to a common sphere of spirituality. Overtones in Tibetan and Gregorian Chant, for example, are linked with spirituality, and even health and well being. Overtones in Tuvan Khomei have at least three different meanings: shamanistic, animistic, and aesthetic.

Figure 13. Mongolia: Ganbold sings a Kevliin Xöömi (ventral Xöömi, similar to Tuvan Sygyt.). The pitch is G3# 208 Hz. The diphonic harmonics are 6th (D#6 1248 Hz), 7th (F#6- 1456 Hz), 8th (G#6 1664 Hz), 9th (A#6+ 1872 Hz), 10th (C7- 2080 Hz), 12th (D#7 2496 Hz). There is a 6 Hz strong vibrato.

Figure 14. Tibetan Gyuto Chant in the Yang style. The pitch is a weak A1 56 Hz. In the beginning, the singer chant a vowel /o/ that reinforces the 5th partial (and the 10th). In the choir part, the articulation of the prayers produces a periodic emerging of all the scale of the harmonics up to the 30th. There is also a fixed resonance at 2200 Hz.

Figure 15. David Hykes and the Harmonic Choir. In this 100 s passage from “Hearing the Solar Winds” [23], the pitch moves slowly from A3, A#3, B3, C4, A3, to the final G3. The diphonic harmonics change in the range 6th-12th.
We would like to thank Sami Jansson [36] and Steve Sklar [15] for the useful information they made available to us via their respective web sites.
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