The laryngeal vibratory mechanisms M0, M1, M2 and M3 refer to the patterns of true vocal fold vibrating behavior that often gave rise to some of the sensations prototypically designated by registers/voices, such as pulse phonation, strohbass, grave, chest voice, mixed voice, falsetto, head voice, flageolet, super head voice, and whistle. Some of these, like super head voice, exist as customized extensions/aspects of other registers/voices. Extensions and aspects refer to specialized versions of a given voice/register. The sensations felt in different voices, registers, extensions and aspects can usually be more concretely correlated with these laryngeal vibratory mechanisms.
In music and speech, humans have long needed to classify the various ways in which the true vocal folds vibrate to produce sound. Before the advent of scientifically visualizing the larynx, first popularized by Manuel Garcia, primitive vocal fold descriptions relied on bodily perceptions secondary to true vocal fold activity at different pitch ranges. Consequently, the classification system based on vocal registers — vocal fry, chest voice, mixed voice, falsetto, head voice, flageolet, whistle register — became commonplace. Each of these is named for perceptions and/or misconceptions about the effects that vocal fold vibrations have on the voice and the body at large. For instance, head register/head voice is believed to be “placed” in the head, while chest register/chest voice is believed to be “placed” in the chest.
As the definition of each vocal register varies drastically between different singers and different vocal traditions, it is hard to use these register/voice terms productively. Alternatively, the concept of laryngeal vibratory mechanisms (LVMs) more objectively correlates with proven vocal fold behaviors.
What is a laryngeal vibratory mechanism?
The laryngeal vibratory mechanisms, which describe the different configurations that the true vocal folds can take independently of pitch range, have concrete borders. Therefore, each laryngeal vibratory mechanism can be thought of as a vocal ‘gear shift’: there are overlaps in range where each may be used, but it’s only possible to use one at a time. Behavior in one LVM can parallel features correlated with another LVM, but there is only one true LVM that can describe the behavior of the vocal folds at any given instance. For example, vocal fold contact pulsations known as “fry” are a constitutive feature of M0, but these pulsations can happen optionally in mechanisms M1, M2 and M3. Using fry in M1 would emulate a feature of M0, but this is not “mixing” with M0. Only one mechanism can be used at a given moment.
As you transition between laryngeal vibratory mechanisms, the vocal folds undergo different behavioral changes. For instance, due to the existing thresholds for these parameters in each laryngeal vibratory mechanism, open quotient increases with the succession of LVMs M0-M3, while closed quotient and recruited vocal fold mass in vibration decrease M0-M3. These changes are realized by varying levels of activation of the cricothyroid, thyroarytenoid, interarytenoid and cricoarytenoid muscles. The activity of these muscles largely controls the adduction and abduction of the vocal folds.
Consequently, these physical changes result in a decay of the harmonic series produced, a decrease in amplitude of the harmonics, with the succession of LVMs M0-M3.
What are the laryngeal vibratory mechanisms?
The different laryngeal vibratory mechanisms, which have distinct common usage ranges and are created by different patterns of vocal fold vibration, can be further subdivided into vocal aspects:
- M0 (?? – D2): pulse phonation, strohbass
- Slack, extended, full-bodied vocal fold motion with vocal fry
- M1 (G1 – A5): grave, chest voice/register, mixed voice
- Modal speech mechanism; majority true vocal fold engagement in vibration.
- M2 (Bb3 – A6): mixed voice, falsetto, head voice/register
- Thinner vocal folds; outer edge (“cover”) engagement in vibration.
- M3 (A5 – ??): flageolet, whistle
- Partial anterior vocal fold tip engagement in vibration.
Further topics in mechanism usage
In the instants of transition between laryngeal vibratory mechanisms, the concrete borders that demarcate and define them often produce what is usually referred to as the pop, passaggio, break or, usually in the case of switching between M1 and M2, yodel. These breaks are defined as the frequency/amplitude jumps and pauses in phonation caused by committed changes in vocal fold configuration between mechanisms. Between different aspects of the same mechanism, one might observe a “pseudopassaggio” caused by changes in vocal fold coordination.
Each laryngeal vibratory mechanism can be further subdivided into different aspects: specialized usages of mechanisms with respect to range and vocal fold configurations.
Roubeau B, Henrich N, Castellengo M. Laryngeal Vibratory Mechanisms: The Notion of Vocal Register Revisited. 2009.
Nathalie Henrich, Christophe D’Alessandro, Boris Doval, Michèle Castellengo. Glottal open quotient in singing: Measurements and correlation with laryngeal mechanisms, vocal intensity, and fundamental frequency. Journal of the Acoustical Society of America, Acoustical Society of America, 2005, 117 (3), pp.1417-1430.
Common usage ranges were inferred from proprioception and spectrographic analysis due to the lack of research on the topic.