First, it’s good to understand how little we understand and that there are no simple answers. Ingo Titze’s Principles of Voice Production book has proven this to me several times. Before I thought that Bernoulli effect explains the vocal fold vibration. However, Titze (2000, 88-89) writes that it cannot explain the vibration by itself. A small thing like vocal folds and their function are such complicated subjects that their proper understanding requires a lot of study. I have to read same chapters again and again. Every time I understand a little bit more. Does it help me to sing better? Not at all! How about teaching? Perhaps. It’s useful to know how things work. Broader understanding feeds creativity and development of new teaching methods. However, you won’t find straightforward answers in books. Or if you do they are usually half truths or speculations. Vocal production can be divided into three parts. Lungs (power), vocal folds (source) and vocal tract (filter). Air flowing out of the lungs makes the vocal folds vibrate which creates sound. Vocal tract amplifies and filters that sound. However, the process is not quite linear. All parts of the system have an effect on other parts. For example, the vocal tract can affect the vocal folds' function and the phonation threshold pressure (Titze & Verdolini Abbott 2012, 286-310).
So what should you know about the vocal folds? I think it’s useful to understand at least that the faster the vocal folds vibrate the higher the pitch. It’s good to know something about the structure of the folds and know they attach to cartilages that move in various ways. I think it’s not that essential to remember which muscle moves which part of the larynx. It’s quite enough if you understand that these parts need to be able to move into different positions. One setting or muscle tension can work for one pitch or sound quality and yet it can be totally wrong and unhealthy for another. There might very well be individual variations and different strategies to produce similar sound qualities.
Many might have heard about CT (cricothyroid) and TA (thyroarytenoid) dominance when talking about registers. To put it simple the idea is that head voice/falsetto/M2 is CT dominant and chest voice/M1 is TA dominant. In order to change smoothly between registers we should increase the activity of one and decrease the activity of the other. Does this help with singing or teaching? I don’t think so. Furthermore it’s wrong! The activity of CT seems to be dependent on the pitch not the register (see Kochis-Jennings 2008 & Hull 2013).
How about muscles of breathing? It could be useful to have a look at the anatomy book in order to get an idea what kind of muscles there are in the torso. Many singers have an incorrect idea about diaphragm so I guess it’s good to know where it is and where it’s attached. It’s more essential to understand how breathing works and what kind of role the diaphragm plays in it. It doesn’t help the singer to sing any better if they know all the latin names of those muscles. And instead of muscles teacher should know the meaning of pressure differences in breathing.
Knowing how the tongue and the jaw move can be helpful in understanding the acoustics of the vocal tract. Personally I don’t remember that many names of the muscles but I know how different parts move. I also know what kind of shapes it is possible to make with the vocal tract. Anyway, concentrating on how a single muscle works is a bad practice strategy. Or have you heard that anyone would have learnt to walk by focusing on their thigh muscles? It’s more important to have an understanding of the acoustics of the vocal tract. You should know the basics of overtones, formants and resonances and understand their function in singing.
Overall, when it comes to details of how our body works I think it’s important to remember what is their function in voice production. The whole is more important than the details. In my earlier blog post I wrote about breathing. It doesn’t matter much how you produce an even sublottic pressure as long as you do it. Of course, in teaching we are usually looking for the least effortful way. I guess the main point of my writing(s) is that there is a lot of information out there and very few things are straightforward. There are conflicting views so the more you read the more you learn to be critical. Eventually that will prove to be useful for both teaching and singing.
References: Hull, Darcey Marie (2013). Thyroarytenoid and cricothyroid muscular activity in vocal register control. University of Iowa. Kochis-Jennings, Karen Ann (2008). Intrinsic laryngeal muscle activity and vocal fold adduction patterns in female vocal registers: chest, chestmix, and headmix. University of Iowa. Titze, Ingo (2000). Principles of Voice Production. Iowa City: National Center for Voice and Speech. Titze, Ingo & Verdolini Abbott, Katherine (2012). Vocology - The Science and Practice of Voice Habilitation. Iowa City: National Center for Voice and Speech