Comparing historical and contemporary opera singers with historical and contemporary Jewish cantors

This study is an attempt to ascertain if singers from different traditions and milieus follow similar aesthetic trends regardless of training and/or background. Cantors who sang the Jewish synagogue liturgy during the Golden Age of cantorial singing prior to World War II came from Eastern and Central Europe. For the most part, they were not trained in the classical Western opera tradition. They received training from choir leaders and other cantors and the training was primarily in the modes of synagogue chant. Cantors today receive the same kinds of training that opera singers receive, often from the same teachers. Four groups of singers, consisting of four singers in each group, were utilized in this study. The four groups are: historical opera singers, contemporary opera singers, historical cantors, and contemporary cantors. The historical opera singer recordings date from as early as 1909 to as late as 1939. It was not possible to determine the dates of the historical cantor recordings. However, the four cantors chosen for this group were active only to the 1940s. Contemporary samples were taken from CDs and/or live recordings and all the singers from the contemporary groups are either still active or were active in the 1960s through the 1980s and all of them are considered to be premier-level singers in their respective areas. The variables analyzed were: vibrato pulse rate, frequency variation of the vibrato pulse above and below the mean sustained sung frequency in percent, the mean amplitude variation of the amplitude vibrato pulse above and below the mean sustained amplitude in percent and the fast Fourier transform (FFT) power spectrum of the sustained samples. Results indicate that most of the significant differences were found between eras and not between groups within a time period.     

Acoustical Comparison Between Samples of Good and Poor Vibrato in Singers

The purpose of this research was to analyze samples of frequency vibrato taken from recordings of eight different singers, which were classified as examples of good or poor singing. The samples were analyzed by a software package, which makes use of the linear prediction coding (LPC) method to determine the time varying rate and extent of the frequency vibrato wave. Four parameters, which relate to the periodicity of the samples, were extracted from the time varying rate and extent and investigated in order to verify or reject the hypothesis that the best vibrato samples were the most symmetric ones. Ten samples per singer were analyzed, 5 good and 5 poor, for a total of 80 samples. The results show that the samples judged as good were the most periodic ones.     

Long-Term Horizontal Vocal Directivity of Opera Singers: Effects of Singing Projection and Acoustic Environment

Vocal directivity refers to how directional the sound is that comes from a singer's mouth, that is, whether the sound is focused into a narrow stream of sound projecting in front of the singers or whether it is spread out all around the singer. This study investigates the long-term vocal directivity and acoustic power of professional opera singers and how these vary among subjects, among singing projections, and among vastly different acoustic environments. The vocal sound of eight professional opera singers (six females and two males) was measured in anechoic and reverberant rooms and in a recital hall. Subjects sang in four different ways: (1) paying great attention to intonation; (2) singing as in performance, with all the emotional connection intended by the composer; (3) imagining a large auditorium; and (4) imagining a small theatre. The same song was sung by all singers in all conditions. A head and torso simulator (HATS), radiating sound from its mouth, was used for comparison in all situations. Results show that individual singers have quite consistent long-term average directivity, even across conditions. Directivity varies substantially among singers. Singers are more directional than the standard HATS (which is a physical model of a talking person). The singer's formant region of the spectrum exhibits greater directivity than the lower-frequency range, and results indicate that singers control directivity (at least, incidentally) for different singing conditions as they adjust the spectral emphasis of their voices through their formants.     

Perceptual and acoustic study of professionally trained versus untrained voices

Acoustic and perceptual analyses were completed to determine the effect of vocal training on professional singers when speaking and singing. Twenty professional singers and 20 nonsingers, acting as the control, were recorded while sustaining a vowel, reading a modified Rainbow Passage, and singing "America the Beautiful." Acoustic measures included fundamental frequency, duration, percent jitter, percent shimmer, noise-to-harmonic ratio, and determination of the presence or absence of both vibrato and the singer's formant. Results indicated that, whereas certain acoustic parameters differentiated singers from nonsingers within sex, no consistently significant trends were found across males and females for either speaking or singing. The most consistent differences were the presence or absence of the singer's vibrato and formant in the singers versus the nonsingers, respectively. Perceptual analysis indicated that singers could be correctly identified with greater frequency than by chance alone from their singing, but not their speaking utterances.     

Inter- and intrasubject changes in vibrato: Perceptual and acoustic aspects

Recent papers by Rothman and Timberlake (1), Rothman (2), Rothman and Arroyo (3), and Keidar, Titze, and Timberlake (4) have focused on the pulse rate, frequency extent, and amplitude extent of vibrato. Some of the emphases of these papers were attempts to clarify the acoustic and perceptual correlates of vibrato, tremolo, and wobble. Rothman and Arroyo (3) speculated that the shape of the frequency variation waveform may be indicative of vocal problems. In order to verify this, we examined recorded segments of sung samples produced by different singers and samples taken from the early and late stages of singers' careers. Some singers had a relatively short career before exhibiting vocal problems. Others had relatively long careers before showing evidence of vocal decline. Many, but not all, of the singers' late career recordings represent examples generally acknowledged to evidence vocal problems/decline. Each sample was digitized at a sampling frequency of 10 kHz, stored, and analyzed using programs reported on by Rothman and Arroyo (3). Data analysis revealed that some parameters can distinguish between good and bad vibrato despite the variance in listener judgments. Furthermore, evidence of vocal decline is not always due to changes in singers' vibrato.     

Level and Center Frequency of the Singer''s Formant

The "singer's formant" is a prominent spectrum envelope peak near 3 kHz, typically found in voiced sounds produced by classical operatic singers. According to previous research, it is mainly a resonatory phenomenon produced by a clustering of formants 3, 4, and 5. Its level relative to the first formant peak varies depending on vowel, vocal loudness, and other factors. Its dependence on vowel formant frequencies is examined. Applying the acoustic theory of voice production, the level difference between the first and third formant is calulated for some standard vowels. The difference between observed and calculated levels is determined for various voices. It is found to vary considerably more between vowels sung by professional singers than by untrained voices. The center frequency of the singer's formant as determined from long-term spectrum analysis of commercial recordings is found to increase slightly with the pitch range of the voice classification.     

Acoustic characteristics of vocal oscillations: Vibrato, exaggerated vibrato, trill, and trillo

Acoustic analysis was performed on recordings of 10 early music singers producing examples of vibrato, exaggerated vibrato, whole-tone trill, and trillo to obtain measures of oscillation rate, frequency extent, and jitter. Oscillation rates for vibrato, exaggerated vibrato, and trill were similar, but trillo rate was much faster. Average frequency extent of oscillation was 1 semitone (st) for vibrato, 2.21 st for exaggerated vibrato, 2.71 st for whole-tone trill, and 1.64 st for trillo. Jitter measures indicated that exaggerated vibrato had the most stable oscillations and trillo the least.     

Measurements of vibrato parameters in long sustained crescendo notes as sung by ten sopranos

Two high-pitched and long sustained notes, F5 and A5, were selected from an aria found in ten commercial recordings of G Verdi's opera Aida by ten different sopranos. Both notes were sung without any instrumental accompaniment and with a crescendo. These audio examples were analyzed with regard to fundamental frequency, vibrato rate, vibrato extent, intonation and sound level, and the relationship among these parameters. The results reveal that vibrato rate differed significantly between the tones in most of the singers and confirm Prame's observations that vibrato rate tends to increase exponentially toward the end of tones. Moreover, both vibrato extent and mean F0 often varied systematically with sound level. The regularity of the vibrato tended to be greater at F5 than at A5.     

Vibrato Rate Adjustment

The goal of the present study was to document the acoustic changes that occur as singers attempt to increase or decrease their vibrato rate to match target stimuli. Eight advanced singing students produced vowels with vibrato in three registers, both naturally and while attempting to match faster or slower rate stimuli. Slower rates were associated with lower intensity and less steady vibrato. Faster rates involved increased vibrato extent in the chest register and increased intensity in the head register. Singers whose spontaneous vibrato rates were naturally either slower or faster tended to also be relatively slower or faster when matching target rates. This ability to modify rate may have beneficial effects on the artistic quality of the voice for performance.     

An electroglottographic study of vocal vibrato

This study investigated vocal vibrato in trained singers through the use of electroglottography (EGG). Ten adult trained singers (7 women, 3 men) were each required to produce four singing tasks. The tasks involved the production of /a/ during an ascending interval of a third in both chest and falsetto registers, once with and once without vibrato. Audio and EGG output during these tasks were directly digitized for subsequent analysis. Results pertaining to changes in the EGG waveform as a function of the singer's gender, the vocal register and the vibrato condition are discussed. A major finding was the apparent absence of consistent, distinctive differentiation in the EGG waveforms when comparing the vibrato and vibrato-inhibited conditions for the majority of subjects. Possible explanations for the majority findings, as well as comment on the feasibility of the EGG for investigating vocal vibrato, are discussed.     

Perception of music performance on historical and modern commercial recordings

Performing styles as well as recording styles have changed considerably within the 20th century. To what extent do the age of a recording, the unfamiliarity with performing style, and the quality of a reproduction of a recording systematically influence how we perceive performances on record? Four exploratory experiments were run to formulate an answer to this question. Each experiment examined a different aspect of the perception of performance, including judgments of quality, perceived emotion, and dynamics. Fragments from Die junge Nonne sung by famous singers from the start, middle, and second half of the 20th century were presented in a noisy and clean version to musically trained participants. The results show independence of perception of emotional activity from recording date, strong dependence of perceived quality and emotional impact on recording date, and only limited effects of reproduction quality. Standards have clearly changed, which influence judgments of quality and age. Additionally, changes restrict the communication between early recorded performers and modern listeners to some extent as shown by systematically smaller variations in communicated dynamics and emotional valence for older recordings.     

Acoustic properties of straight tone, vibrato, trill, and trillo

Recordings were made of four internationally acclaimed early music singers (two women, two men) as they sustained phonation at target frequencies while producing the vocal ornaments straight tone, vibrato, trill, and trillo. Recordings were analyzed for the presence and amount of fundamental frequency oscillation and the frequency location of the vocal ornament performed with respect to the target tone. Results showed great variability between singers in all measured parameters.     

Discrimination Functions: Can They Be Used to Classify Singing Voices?

Researchers long have searched for invariant acoustic features that can be used to identify singing voice categories or even individual singers. Few researchers have examined how listeners perceive singing voice categories or individual voices. Timbre, the most studied perceptual dimension of the singing voice, is generally believed to vary systematically between singing voice categories but is often assumed to be invariant with an individual singer. To test this assumption, 2 mezzo-sopranos and 2 sopranos were recorded singing the vowel /a/ on the pitches A3, C4, G4, B4, F5, and A5. Trials of three stimuli were constructed. Two of the three stimuli in each trial were produced by the same singer at two different pitches (X₁ and X₂), while the third stimulus was produced by a different singer (Y). Three X₁X₂ conditions were created: (1) G4, B4; (2) C4, F5; and (3) A3, A5. For each singer and each condition, Y was varied across the three remaining singers and across all six pitches. Experienced and inexperienced listeners were asked to identify which stimulus was produced by the “odd” person. The ability to correctly choose the odd person varied greatly depending on pitch factors, suggesting that the traditional concept of an invariant timbre associated with a singer is inaccurate and that vocal timbre must be conceptualized in terms of transformations in perceived quality that occur across an individual singer's range and/or registers.     

Vibrato and pitch transitions

There are at least two timing variables to be considered in vocal music performance. The first is the note changes associated with the meter signature (4/4, 2/4, etc.) and the second is the vibrato rate of the performer. Because the probability is not great that these two temporal variables will always be in perfect synchrony, it was the purpose of this investigation to determine what singers do when these two timing variables come into conflict during singing. Six singers recorded a series of alternating upward and downward interval shifts of a third while singing whole notes, half notes, quarter notes and eighth notes. The same notes were then recorded with intervals of a fifth. The recorded samples were converted to a visual trace and examined for interactions between vibrato and meter. Analysis of the tracings indicated that, in the majority of the cases, the singers would alter their vibrato in order to adhere to the timing of the musical line.     

MELISMA SINGING AND PREFERRED STAGE ACOUSTICS FOR SINGERS

Vocal performance characteristics, such as tempo, colour, and expressiveness of singers are part of the unique artistic impression of individual performers and individual performances. Subjective pair-comparison studies of singers in a previous study demonstrated that singers prefer added reflections with delays in the range of 10-20 ms. However, the range of values between singers, for the effective duration of the autocorrelation of the singer's voice, was limited, and insufficient to demonstrate a relationship between individual vocal characteristics and the preferred delay time of reflections. In this study, to investigate the singer's preferred acoustics with a change in singing style, subjects were asked to perform non-plosive, non-fricative text for the lyrics, using exclusively “la” syllables (melisma singing). A resulting shift in preferred time delay was observed. The extent of the shift in preferred reflection time delays is shown to be directly related to the minima of the effective duration of the running autocorrelation function calculated from each singer's voice. Singers were also subjected to training, to assist in identifying sound fields. After training, the average preferred delay time of the reflection did not change, but the statistical variability of the singer's subjective rating of the sound fields was strongly reduced.     

Long-Term-Average Spectrum Characteristics of Country Singers During Speaking and Singing

Five premier male country singers involved in our previous studies spoke and sang the words of both the national anthem and a country song of their choice. Long-term-average spectra were made of the spoken and sung material of each singer. The spectral characteristics of county singers' speech and singing were similar. A prominent peak in the upper part of the spectrum, previously described as the "speaker's formant," was found in the county singers' speech and singing. The singer's formant, a strong spectral peak near 2.8 kHz, an important part of the spectrum of classically trained singers, was not found in the spectra of the country singers. The results support the conclusion that the resonance characteristics in speech and singing are similar in country singing and that county singing is not characterized by a singer's formant.     

从表演者角度论述歌剧院的声学研究和设计

本文从解决歌手与乐队竞争的谜团入手,详述了歌剧院乐队演奏(缺乏高频声)和歌剧唱法(高频的歌手共振峰)的声音特点,进而提出了歌手和乐队之间平衡的声学设计(即放大歌手的歌唱声并适当降低乐队的演奏声,观众听起来歌手和乐队之间的声音保持平衡),重点论述了乐池的声学设计。然后分别从提高表演者的相互听闻(为了合奏的同步性)和提高房间的声反馈(为了控制演奏的响度)进行了论述,得出从表演者角度进行声学研究和设计的重要性。     

Acoustic analysis of the singing and speaking voice in singing students

The singing power ratio (SPR) is an objective means of quantifying the singer's formant. SPR has been shown to differentiate trained singers from nonsingers and sung from spoken tones. This study was designed to evaluate SPR and acoustic parameters in singing students to determine if the singer-intraining has an identifiable difference between sung and spoken voices. Digital audio recordings were made of both sung and spoken vowel sounds in 55 singing students for acoustic analysis. SPR values were not significantly different between the sung and spoken samples. Shimmer and noise-to-harmonic ratio were significantly higher in spoken samples. SPR analysis may provide an objective tool for monitoring the student's progress.     

Modal Distribution Analysis, Synthesis, and Perception of a Soprano''s Sung Vowels

A high-resolution time-frequency analysis technique, the modal distribution, is applied to sung vowels from a soprano singer. Parameters are estimated for each partial component of notes analyzed with the modal distribution. These estimates are used in an additive synthesis model to generate replicates of the original recording, using a series of time-varying sinusoids. Additionally, a source-filter model is applied to create synthetic signals, where pitch- and vowel-specific filters and driving functions are constructed from the amplitude and frequency estimates obtained. Different driving functions, which sample the range of this singer's rate and excursion variation, are transposed and filtered to create synthetic signals. The perceptual salience of the different rates and excursions is then determined via a paired-comparison listening experiment. It is found that listeners are sensitive to small variations in both average vibrato rate and average vibrato excursion. However, the perceived amount of vibrato excursion varies somewhat depending upon the pitch at which the vibrato is “played” synthetically. Finally, the naturalness and sound quality of these synthetic examples is determined through both paired-comparison and single-note sound quality scaling listening experiments.