Is the degree of posterior glottal adduction relevant for “voix mixte” phonation?

Christian Herbst, Jan G. Švec

In the context of a voice coaching situation, a 52 year old semi-professional baritone was diagnosed to have a limited upper range. Starting with a pitch of about C4, the phenomenon of divergent registers occurred: with increasing pitch, phonation was only possible in either loud chest voice, or falsetto phonation. Messa-di-voce exercises in the range between Bb3 and F#4 exhibited register breaks in both the crescendo and decrescendo. The full chest voice reached its pitch limit at about 365 Hertz. Even though a voice range profile revealed a dynamic range from 72 to 114 dB at pitches from C4 to F4, the region between 94 and 102 dB could hardly be used for artistic purposes at those pitches.
An a priori stroboscopic examination revealed a habitual increase of the degree of posterior glottal adduction at pitches at and above C4. It was hypothesized that a lesser degree of posterior glottal adduction could increase the artistically usable pitch and dynamic range.
In order to test this hypothesis, the baritone was asked to sing various exercises while having constant visual feedback through videostroboscopic imaging. The arytaenoids were targeted to be spread slightly apart during phonation in the upper range. The targeted acoustic quality was described as “almost breathy”.
When phonating in the upper pitch range with a lesser degree of posterior glottal adduction, the cartillagenous portion of the vocal folds became visible. The arytaenoids changed their position, suggesting active participation of the posterior cricoarytenoid muscle (PCA). The ventricular folds were slightly more retracted, thus widening the epilaryngeal tube. Immediately after the session with the visual feedback, the baritone was able reach pitches as high as Bb4 without audible register breaks. The SPL was within the previously missing range of 90 to 100 dB. Electroglottographic evidence revealed a decreased waveform width, signifying a decreased duration of glottal closure as opposed to phonation with a high degree of posterior glottal adduction.
The findings suggest that posterior glottal adduction is an important physiological parameter in singing. It allows achieving a specific voice quality which is perceptually and dynamically between the chest and falsetto registers and thus could be considered to correspond to that of a “voix mixte” tone production.

Christian Herbst (herbst@ccrma.stanford.edu)
Tölzer Knabenchor, Munich/Germany
Jan G. Švec (j.g.svec@med.umcg.nl)
Groningen Voice Research Lab, Biomedical Engineering Dept., UMCGroningen