Preferences for Strong or Weak Singer's Formant Resonance in Choral Tone Quality

The purpose of this study was to assess the preferences of undergraduate college student auditors (N = 139) with respect to a choral sound produced in an anechoic chamber that included a fully resonate singer’s formant and choral sound produced in the same chamber using a weaker singer’s formant resonance. An ensemble comprised of graduate voice students (N = 8) sang four choral music excerpts. Each excerpt was recorded twice. Singers first employed a full soloistic placement that resulted in a tone with strong upper resonance in the singers’ formant range (2 kHz – 4 kHz). The same singers then employed a greatly reduced singer’s formant resonance. Recordings were analyzed, then compiled into a stimulus recording for this study. Auditor participants were randomly assigned to one of two listening groups. One group listened to six pairings each of two of the choral music excerpts for a total of twelve trials. For each excerpt, the order of presentation of the non-resonant version versus the resonant version was presented three times in one order and three times in the reverse order. Each of the six trials was randomized with the six trials from the second choral music excerpt. The same procedure was followed for the second two choral music excerpts. In each trial, subjects were asked to indicate that excerpt performed with the tone quality that they liked the best. Responses were cross-tabulated according to participants’ musical training: (a) college undergraduate choral or vocal music majors with choral training (N = 49), (b) college undergraduate music majors with instrumental training but no choral training (N = 47), and (c) college undergraduates with no music training (N = 43). Results indicated a significant difference (p < .000) between preferences for non-resonant and resonant tone quality. Examination of the mean scores revealed that auditors overall preferred a non-resonant tone quality (M = 7.95) over a resonant tone quality (M = 4.05). When the three training groups were used as factors, a significant difference of (p < .000) was observed between the choral training group and the instrumental training group. There was also a significant difference (p = .001) between the choral training group and the no music training group. The difference between the instrumental training group and the no music training group was not significant (p = .998). Such results appeared to suggest that not only did most auditors prefer a non-resonant choral tone to a resonant one, but also that choral training seemed to increase that preference. Although results were limited to the particular conditions, participants, and choral music excerpts of this study, these findings were discussed in terms of possible ramifications for choral pedagogy and directions for future research. Choral tone quality is a topic of both interest and debate among choir conductors and voice teachers. Whether it is preferable for choir singers to sing with a fully resonant or less resonant tone quality frames a part of this ongoing discussion, particularly with respect to use of those notably strong resonance frequencies within the vocal tract known as the singer’s formant. According to Sundberg (1988b), singer’s formant resonance is “a prominent spectrum envelope peak appearing in the range of 2 to 4 kHz in all vowel spectra sung by male singers and also by altos. It belongs to the typical features of a sung vowel” (p 14). Ford (2003) International Journal of Research in Choral Singing, Vol. 1 (1) Singer’s Formant 30 In 1863, Hermann L.F. Helmholtz (1821-1894) employed reference to a choral singing context to discuss what would later become known as the singer’s formant. Helmholtz (1954), building on a vowel theory based on the length of reed pipes as advanced by Willis in 1830 and the vowel formant theory offered by Wheatstone in 1837, identified the frequency range of what he then termed “tinkling” or “partial tones” as between 2640 to 3168 vibrations per second (Hz). According to Helmhotz: In powerful male voices singing forte, these partial tones sound like a clear tinkling of little bells, accompanying the voice, and are most audible in choruses, when the singers shout a little. Every individual male voice at such pitches produces dissonant upper partials...If many voices are sounding together, producing these upper partials with small differences of pitch, the result is a very peculiar kind of tinkling, which is readily recognized a second time when attention has been once drawn to it... I have never heard it from any other musical instrument so clearly as from human voices (p 116). Monohan’s (1978) survey of writings on the teaching of singing between 1777-1927 indicated comparatively few references to resonance prior to Helmholtz’ work. Fillebrown (1911), while recognizing proliferating opinions on the matter, stated that systematic research was needed: “the basic importance of resonance in the use of the voice is still too little recognized, though obvious enough in the construction of musical instruments” (p 43). Witherspoon (1925) perhaps summed up the frustration still occasioned by this topic when he said: “probably not even the question of breath has caused more dire confusion and uncertainty, not to speak of faulty emission of voice, than this comparatively new bugaboo, RESONANCE!” (p 21). With respect to individuals’ use of the singer’s formant resonance in a choral singing context, the literature of the past five decades is replete with a rich variety of perspectives from choral conductors, choral methods texts, and vocal pedagogy materials. Such writings, however, are largely anecdotal, and may lack the credibility afforded by more systematic, controlled research. Scientific Studies of Singer’s Formant Resonance in Individual Voices Scientific studies of the solo voice have indicated that full upper resonance in the singer’s formant range is one of the components that is preferred for a solo voice quality to be judged as good (e.g., Bartholomew, 1934; Bloothooft & Plomp, 1986; Bloothooft, 1987). Among the early scientific investigations of formants, Paget (1922) explored different resonating cavities in the vocal tract. In that report, he referred to vocal formants, or, more specifically, vowel formants, as “resonance notes’ (Paget, 1922). Bartholomew (1934) observed that a large concentration of energy in the frequency region between 2400 and 3200 Hz was characteristic of good voice quality. Albert (1951) concluded that the relative, as opposed to absolute, dimensions of the vocal tract determined formant frequencies. Arment (1960) found that perceived brightness of a vowel depended upon the strength of high partials and narrow formant bands, while perception of vowel darkness depended upon broad formant bands and the lack of high partials. Gunn (1960) indicated that brightness and darkness were directly impacted by the frequency of the first two formants, the intensity of the second and third formats, and the intensity of the harmonics in the range of 2800 cps (Hz). Rzhevkin (1956) reported detecting singer’s formants in the regions from 500 to 2500 cps (Hz). He found upper formants were not as clearly defined in an untrained singer as in a trained singer, and that the highest formant was missing in the untrained voice. Delattre, Liberman, Cooper and Gerstman (1952) published an article entitled “An experimental study of the acoustic determinants of vowel color; observations on oneand two-formant vowels synthesized from spectrographic patterns.” These researchers used a pattern playback machine to play the results of hand-painted spectrographic patterns in an attempt to determine the effect of various acoustical features on the vowel sound produced. They then modified various formants and reported the resulting changes in subjects’ perceptions of the vowel and vowel color. Vennard and Irwin (1966) contrasted the acoustical aspects of singing to speech by comparing the sonograms of spoken and sung versions of a secco recitative. Among other findings, a difference in the formant in the vicinity of 3000 Hz was noted. Vennard and Irwin referred to this formant as the 2800, due to the fact that 2800 Hz seemed to be an average location of the formant. The authors stated that this formant Ford (2003) International Journal of Research in Choral Singing, Vol. 1 (1) Singer’s Formant 31 produced the “ring” in the singing voice. Teie (1976) concluded that the development of the singer’s formant is related to the amount of vocal training. He also noted that even the untrained voices in his study possessed resonance in the singer’s formant range when an [i] vowel was employed. Magill and Jacobson (1978) examined various vowels at different pitch levels as produced by 22 singers of various voice types, both college students and professional singers. They concluded that the singer’s formant may be present in all voice types, but that the intensity of the singer’s formant was subject to training. Schultz-Coulon, Battmer and Riechers (1979a, 1979b) explored the dependency of the relative amplitude of the singer’s formant on pitch and intensity. They found that with untrained singers the relative amplitude of the singer’s formant appeared to grow as vocal intensity increased and diminish as the pitch rose. This factor was more pronounced with the male voices than the female voices. Trained voices appeared to have more energy in the singer’s formant range, though not for all pitches. In both trained and untrained voices, the singer’s formant intensity appeared stronger in male voices than in female voices. Seidner, Schutte, Wendler and Rauhut (1985) found that female singers in their investigation generally had two peaks in the spectrum in the singer’s formant range. One occurred between 2500 and 3000 Hz and the other occurred between 3000 and 4000 Hz. They also found that the male singers in that study had a higher relative intensity and narrower bandwidth of the singer’s formant Bloothooft and Plomp (1986) sought to measure the sound level of the singer’s formant in professional singers. They found almost no difference in sound level between male singers (4 dB). However, they did find a greater sound difference in female singers (24 dB). Wang (1985) compared singers with specialties in western operatic singing, Chinese singing, and western early music singing. Singers appeared to evidence the spectrum peak in the range attributed to that of the singer’s formant, but did so with varying larynx heights. Wang concluded that a low larynx was not the only method of producing a bright timbre. Sengupta (1990) examined singer’s formant in North Indian classical singing and found that the center frequency of the singer’s formant and the resonance balance rose with the frequency of the fundamental. Nawka, Anders, Cebulla and Zurakowski (1997) observed a male “speaker’s formant,” i.e., a spectral peak near the level associated with the singer’s formant. The Sundberg Studies Johan Sundberg has researched the singer’s formant for over thirty years. The following studies, in particular, have contributed to current understandings of phenomena associated with singer’s formant. Sundberg (1968) investigated the formant frequencies in a bass singer. He suspected that the larynx was the source of the singer’s formant in this individual. Sundberg (1972a) explored an articulatory interpretation of the singer’s formant. Findings suggested that a lowered larynx, as revealed by tomogram data, increased the laryngeal ventricle, the sinus piriformes, and the crosssectional area, which produced a resonating chamber that would appear to be the source of the singer’s formant. Sundberg also suggested that the singer’s formant was produced acoustically by a clustering of the third, fourth, and fifth formant frequencies. Sundberg (1972b) took an average spectrum from an orchestra playing alone and from an orchestra accompanying a singer. There was a pronounced peak in the 2800 Hz range when the singer was singing. This singing formant peak seemed to be the spectral component that enabled the human voice to project through the orchestral sound. In exploring perceptual aspects of the solo singing voice, Sundberg (1979) noted that the singer’s formant and pitch dependent formant frequencies were both responsible for audibility of the voice over loud orchestral sounds. He suggested that vocal economy allowed some resonatory phenomena to occur independently of vocal effort. Sundberg (1994) investigated two qualities important to solo singing. Vowel quality, suggested Sundberg, was determined by the lower two formants. Vocal quality was determined by the higher frequency components, specifically the center frequency of the singer’s formant. Sundberg stated that while singer’s format could be found in male voices and alto voices, it appeared not to be present in the soprano voice. He did caution that the studies had used measurement tools that had fixed and narrow band-pass filters and that if the soprano singer’s formant was much higher or much broader in frequency it might have gone undetected. Sundberg (1999) suggested that sopranos used a method of formant tracking to boost the projecting power of their voices in absence of a singer’s formant. This tracking occurs when the fundamental frequency approaches and passes that of the lowest formant frequency. The singer then adjusts her mouth opening wider and raises the lowest formant, keeping it in close proximity to the fundamental tone. Ford (2003) International Journal of Research in Choral Singing, Vol. 1 (1) Singer’s Formant 32 Sundberg stated that the lower voice categories of alto, tenor, baritone, and bass did not need to use the formant tracking procedure because they were able to cluster the third, fourth, and fifth formants and produce the singer’s formant. According to Sundberg, this procedure of clustering the formants does result in the modification of the vowels but not in the same manner as the formant tracking procedure. Scientific Studies of Solo Voices in a Choral Situation Other studies have focused upon individual voices in a choral situation. Harper (1967) recorded individual subjects while they were singing in a choir by using close microphone techniques. Results, from spectrograms and auditor responses, indicated no consistent differences between solo and choral singing for the first two formant frequencies. There were, however, differences in the amount of energy located between formants. Goodwin (1977) found that sopranos instructed to sing vowels in a “blended mode” tended to have lower intensity levels, stronger fundamental frequencies, fewer and weaker upper partials, and stronger first formants than when singing in a “solo mode.” Rossing, Sundberg, and Ternström conducted two studies in 1985 that investigated the solo versus the choral voice. The researchers noted that sopranos sang with more intensity in the singer’s formant range and with a slightly greater vibrato extent in solo mode compared to choral mode (Rossing, et al 1985a). They also found that with bass and baritone singers the strength of the singer’s formant was greater and the fundamental weaker in solo singing than it was in choral singing. The lower-voice men seem to cluster their third, fourth and fifth formants in order to strengthen the singer’s formant (Rossing, et al, 1985b). Scientific Studies of Choir Acoustics In his 1989 dissertation, Sten Ternström investigated acoustical features of choir singing with a series of studies. Among Ternström’s findings were several items relevant to consideration of singer’s formant in choral contexts. One study investigated the intonation precision and the vowel articulation of singers in a choir. Ternström found that intonation was affected by the aural feedback that singers received from the physical environment, which included the singer’s own voice and the voices of the rest of the chorus. He also found that singers from one choir used different vowel articulations in choral singing than they used in speech and, to a lesser extent, in solo singing. Another study concluded that choirs adapted sound level and vocal technique to the acoustics of the room, and that room acoustics affected the longtime (or long-term) average spectrum (LTAS) of choir sound. In a third study, Ternström investigated flutter by means of synthesized vocal sound. Flutter is the natural frequency variation that is present in the human voice. He found that without flutter, synthesized voices sounded more like a “mediocre electric organ” than a chorus; however, with the presence of flutter, the synthesized chorus sounded realistic. In discussing vocal tone quality, Ternström made reference to the singer’s formant. Ternström stated that this “singer’s formant ...would defeat choral blend, unless it is used by most or all of the choir members.” He also stated that through his research he had only rarely recorded an experienced chorus singer singing with a pronounced singer’s formant. In a separate study, Ternström investigated the formant frequencies of eight bass choir singers in an effort to discover whether or not these singers altered their formant frequencies from those used in normal speech and those used in an attempt to blend with other voices. None of these bass choral singers sang with a pronounced singer’s formant. Ternström, however, noted a difference between the vowel formants used for speech and those used for singing. In brief summary, the literature suggests that the particular resonance phenomenon known as the singer’s formant: (a) occurs in vowel spectra of the 2 –4 kHz range among male and alto singers (while sopranos may use to similar effect a method of formant tracking); (b) has its physical source in a resonating chamber produced within the human vocal tract that may or may not be aided by laryngeal height; (c) is developed through practice and training as an efficient and economic means of vocal projection; (d) contributes to the vocal quality of solo voices as having “ring” or “ping;” and (e) does not appear to be ordinarily employed when singing in a choir by either amateur choral singers or those trained singers previously experienced in choral singing. Despite such indications, voice teachers and choir directors continue to debate the use of singer’s formant in choral singing, frequently confusing it with other phenomena and sometimes applying it to larger debates about so-called “straight tone” or “blended” singing. Such controversy often appears to have a life of its own, quite apart from scientific findings. In this sense, the issue has become a Ford (2003) International Journal of Research in Choral Singing, Vol. 1 (1) Singer’s Formant 33 matter of some practical import, particularly for choir directors who may be told that they are impeding the singing of voice students asked to sing chorally with less resonance and for voice teachers who fear that their students may be harmed by such practice. Smith (2002), for instance, in an article that frames the debate from the perspective of a voice teacher, contends that audiences prefer a robust choral sound where all singers employ the singer’s formant. To date, however, no empirical studies have investigated auditor preference with regard to a conglomerate, choral sound where all singers simultaneously employ a full singer’s formant resonance (or, in the case of sopranos, formant tracking). The present investigation is framed to examine such contentions.