Glottal behaviour, resonance tuning and the upper limit to the high soprano range
Résumé
Twelve sopranos (4 non experts, 4 advanced, 4 professionals) produced glissandi up to their highest note (from 1000 to 2300 Hz). Later, they sustained pitches on [a] vowels, from A4 (~440 Hz) to their highest sustainable note. Between C5 and G5, all singers demonstrated a significant decrease in amplitude of the electroglottograph signal with increasing pitch, together with a change in waveform. This modification in glottal contact was either continuous, over a few tones range, or discontinuous, accompanied on glissandi by a pitch jump. Two singers could vary the pitch of this transition and therefore presented an overlap range over which they could produce either a 'full head' or a 'fluty' quality. Transition from one quality to the other on the same note was discontinuous and accompanied by a pitch jump. No other significant modification in glottal contact was observed at higher pitch. The frequencies (R1 and R2) of the first two vocal tract resonances were measured by broadband excitation at the mouth. Adjustment of R1 near to f0 (R1:f0 tuning) was observed below C6 for both expert and non-expert singers. Experts began this tuning at lower pitches. Some singers also exhibited R2:2f0 adjustment over the lower part of the R1:f0 tuning range. In the very high range (above C6), the singers used one of two strategies. Some extended the R1:f0 tuning as far as E6 or F#6. Others adjusted R2 near f0 over the highest pitch range (up to D7). The limit of the sustainable range corresponded to the end of these resonance tunings. This strongly suggests that the upper limit of their useful singing range was determined by the upper limit of one or other resonance tuning mechanism. Further, it seems likely that learning R2:f0 tuning might extend the practical upper range of some sopranos.