Tiny Folds, Big Sounds: The Physiology of Singing

Marissa Simmons is a professional opera singer and private music teacher in the Chicagoland area.  During her studies at the University of Miami Frost School of Music and the San Francisco Conservatory of Music, Marissa studied the anatomy and physiology of the vocal folds extensively in order to get a biological perspective on proper vocal technique.  This week, Marissa sat down the with the editors of Science Unsealed to give them some tips about what the vocal folds do and how they function differently for opera, screamo, and yodeling.

Who are you and what do you do?

I’m an emerging professional operatic mezzo-soprano. I am also a private music teacher for voice, piano, music theory, composition, and violin. I am the Director of the OTA Music Studio.

What path (education, life experience, etc.) led you to where you are now?

I have earned a Bachelors Degree in Classical Voice Performance, Music Theory, and Composition as well as a Masters Degree in Opera. I currently sing with many small opera companies in the Chicagoland area.

What anatomy is involved with general phonation?

Muscles around the Larynx

Phonation refers to making vocal/speech sounds.  To phonate we inhale, and then as we exhale, we make our vocal folds vibrate at a particular rate to determine the pitch level of our voice. Actual phonation almost solely involves the vocal folds and the other small muscles and cartilage in the larynx.  

What do the vocal folds do? How do they move?  Do muscles control them? How does their frequency correlate with the pitch of the sound produced?

The actual biological purpose of vocal folds is to help prevent choking, as well as to help lift heavy objects, excrete waste, and give birth (activities that require applying pressure below your waist). It is amazing that vocal folds can make the sounds they do, and it’s often surprising to people that phonation is not their primary purpose by a long shot.

The vocal folds move like a wave as they adduct (come together) and abduct (come apart) as air blows through them. To sing the pitch A440, the standard pitch used to tune string instruments, the vocal folds vibrate at 440 times per second. The vocal folds are controlled by tiny muscles in the larynx called the thyroarytenoid muscles and the cricothyroid muscles.

These muscles play a large part in changing of pitch of our voice from low to high. They cause the vocal folds to thicken or elongate, like stretching a rubber band or a string on a violin.

The thinner the string on the violin, the faster it vibrates, and the higher the pitch. The thicker the string on the violin, the slower it vibrates, and the lower the pitch. One of the things that can make “singing in tune” quite difficult for many people is the fact that we can’t actually directly control the cricothyroid and thyroarytenoid muscles. Instead, vocalists use lots of different exercises to help navigate through the different parts of their vocal range and naturally engage those muscles. Every note we sing or speak uses a slightly different balance of those two muscle sets.

What are the vocal folds doing during vibrato?

The vocal folds don’t actually have much to do with vibrato. You can sing the same pitch with and without vibrato and your vocal folds will still vibrate the same way. Unfortunately, science has yet to crack the code to what exactly causes vibrato, but here’s what we do know: we naturally sing with vibrato when our larynx muscles are relaxed. In other words, when someone is getting really good at singing, they start to sing vibrato in vibrato without thinking about it. Healthy vibrato is said to oscillate at about seven times per second, though it often oscillates faster for younger singers. Fast, but consistent vibrato, is a sign that someone’s voice is in its natural state. If someone’s vibrato speeds up and slows down, its likely that their muscles are still a little bit tense. When someone sings a slow vibrato, its often that he or she has a tense tongue or jaw that isn’t allowing sound to escape as freely as it should.

How fast can the vocal folds open and close? How slow? How does this compare to the speed of a hummingbird’s wings fluttering?

When you breathe, your vocal folds open. If you can hold your breath without tightening your throat, chances are your vocal folds can stay open however long you’re holding your breath. Vocal folds easily vibrate from around 65 times per second (Hz) for low bass voices to 1760 Hz for the highest treble voices. 65 Hz results in a low C (C2) for a bass and 1760 Hz results in an A above high C (A7) for a soprano (the highest pitch ever sung at the Met). A hummingbird’s wings, depending on the specific type, can range from about 10-50 Hz, much slower than our vocal folds.

Do opera, screamo/death metal, and yodeling use this anatomy differently?

Opera focuses on using the anatomy at its most efficient by using the instrument in its freest manner so the singer can make as beautiful a sound as possible.

Screamo, if done correctly, doesn’t even use the vocal folds. If a screamo singer uses their vocal folds, they will wreck them in a jiffy. Proper Screamo technique actually uses the musculature around the vocal folds and the “false vocal folds” which reside above the actual vocal folds. The following video shows the vocal folds moving while singing the vowel “e” and then the false vocal folds moving during throat singing and various screamo sounds (0:00-0:31).

The Larynx

When done correctly, the actual vocal folds hardly move.

Yodeling involves switching from “chest voice” to “head voice” abruptly and frequently. Basically, when you’re yodeling you use either the cricothyroid muscles or the thyroarytenoid muscles, not both at the same time, like in normal singing. The cricothyroid muscles are more involved for “head voice” and the thyroarytenoid muscles are more involved for “chest voice.”

How do hormones affect the development of the vocal folds and different voice parts? What about Castrati?

Estrogen thins the vocal folds and raises the natural pitch level of a person’s voice and testosterone thickens the vocal folds, lowering the natural pitch level. As hormone levels change throughout life, they will undoubtedly affect the voice. Castrati were castrated before or right at the beginning of puberty, so they didn’t have the typical testosterone levels of grown men. This, in turn, caused their adult bodies to develop much differently, and of course, their voices developed differently too. They were often very tall, overweight, and had unbelievably large chests with over-sized rib cages. All of these factors gave them a sound that simply cannot be produced by a natural human. We can attempt to make similar sounds today, but it is still not the same. The closest naturally occurring voice type is the countertenor, of which Chris Colfer, who played Kurt on Glee, is an example.

Castratos were common between the mid-1500s to the mid-1800s until it was made illegal in Italy. Here is a recording of the last living castrato and the only castrato ever recorded:

What is a coloratura and how do their vocal folds move differently from non-coloratura singers?

Coloratura is a subcategory of voice types that refers to voices that are particularly agile and can sing runs and trills with great clarity and speed. It can also refer to a type of repertoire or a type of musical passage with the same characteristics as listed above. A voice that is defined as a coloratura soprano or a coloratura mezzo just implies that that voice loves to move quickly and does it with ease. These voices tend to sing repertoire by composer like Rossini or Händel because those composers wrote lots of coloratura-filled arias. For coloratura voices, the vocal folds are more flexible in their ability to change their vibration speed rapidly. Coloratura has nothing to with the vocal folds, but often the size of the voice is different. People with dramatic voices or giant voices often have more difficulty singing fast passages than slightly smaller voices, but nevertheless, all voice types have to learn to move and be agile.

Further Reading:

On the vocal anatomy: “Why is there a frog in my throat? A Guide to Hoarseness.” by James P. Thomas, M.D.

Originally from Chicago, Marissa Simmons is noted for her “rawly sensual, wry, whiskey-toned voice” (San Francisco Classical Voice). She is also distinguished by her “deep, evenly produced mezzo and theatrical magnetism” (South Florida Classical Review) and praised as an“elegant and full-voiced mezzo-soprano” (San Francisco Chronicle). Twitter: @MarissaMezzo, Facebook: Marissa Simmons, mezzo-soprano.