So you’ve read our article on the four laryngeal vibratory mechanisms and you start thinking about the mixed voice. You start wondering…. surely, since people say that mixed voice is a mix between chest voice (usually considered to be in M1) and head voice or falsetto (usually considered to be in M2), it must be a register between M1 and M2… so M1.5.

The existence of a M1.5 is a very prevalent myth. Plenty of people think that mixed voice is a distinct mechanism of vocal fold vibration, i.e., a distinct register. But M1.5 doesn’t actually exist.

If you’ve read our article on the Power-Source-Filter Model of Voice Production, then you know that the vocal folds can be divided into three layers: the body, the transitional layer and the cover. There’s one fundamental difference between M1 and M2: in M1, both the body and the cover of the vocal folds vibrate; whereas in M2 only the cover vibrates.

So, when you’re doing a glissando from chest voice to head voice, at some point, the body of your vocal folds is going to stop vibrating. At that point, you’re instantly in M2 because only the cover is vibrating. There’s no transitional mechanism, no M1.2, no M1.3, no M1.5. It’s this instant break from M1 to M2 that can make that cracking sound we’re all too familiar with. When, on purpose, you don’t disguise this break, it’s called a yodel or a flip.

But then why don’t all transitions from M1 to M2 produce a yodel? Trained singers are able to disguise this break when they want to give the illusion of a sound that’s fully connected throughout their range. In order to explain how they do this, we need to introduce the concepts of open quotient (OQ) and closed quotient (CQ).

• Open Quotient (OQ): the ratio of the duration of the open phase (when the glottis is open in each cycle of vibration) to that of the duration of each complete cycle of vibration; in simpler terms, it’s a cyclic measure of how long the vocal folds stay apart.
• Closed quotient (CQ): the ratio of the duration of the closed phase (when the glottis is closed in each cycle of vibration) to that of the duration of each complete cycle of vibration; in simpler terms, it’s a cyclic measure of how long the vocal folds stay together.
  
  Closed quotient is calculated with the formula 1 – OQ, therefore, a high closed quotient implies a low open quotient and vice-versa. In more practical terms, a higher CQ produces a buzzier sound at the vocal fold level. A word of caution: you can’t say you’re “in an open quotient” or “in a closed quotient”, that’s like saying you’re in a frequency. You can however, say that you’re using a high OQ or a low OQ.

Now we’re able to actually understand how singers are able to, when they want to, navigate their M1-M2 range without a noticeable break.

On a glissando from chest voice to head voice, by slowly increasing the open quotient, they’re able to lighten their voice, making it more tonally similar to M2, yet the body of the vocal folds (the vocalis muscle) is still vibrating in sync with the cover, so it’s M1. When the transition actually occurs, the similarity in tonal quality hides the break, but it’s still there (and can almost always be picked up by a trained ear). The body and cover of the vocal folds decouple from each other, leaving only the cover vibrating, producing a spike in frequency (which is also usually hidden by decreasing the volume and reduced with training). The exact opposite thing happens on downward glissandi from head voice to chest voice.

By (its very vague) definition, mixed voice encompasses both part of M1, where it takes the notation of mx1, and part of M2, where it takes the notation of mx2. The m doesn’t stand for mechanism, it’s just the m in mix.

So, does mixed voice exist? Is it a vocal register? I’d say that the answer to that question doesn’t matter. What matters is knowing that M1.5 doesn’t exist, that mixed voice isn’t a distinct pattern of vocal fold vibration and that mixed voice can’t be exactly defined (there’s no one point at which you can say you’re in mixed voice or not in mixed voice, unless you’re in M0 or M3).

This also means that you don’t have to “find your mix”. It’s not a mechanism you have to find. It’s just a matter of lightening/darkening your voice so as to disguise a physiological break in your voice when transitioning between laryngeal vibratory mechanisms.

References

Sylvain Lamesch, Robert Expert, Michèle Castellengo, Nathalie Henrich Bernardoni, Bertrand Chuberre. Investigating voix mixte: A scientific challenge towards a renewed vocal pedagogy. 3rd Conference on Interdiciplinary Musicology, CIM07, Aug 2007, Tallinn, Estonia. ffhal-0020799