How the voice works · Vocal folds
CT and TA, the registration muscles
How the stretcher and the thickener share the work of pitch and registration, drawn slowly and labelled. Then see the same folds in 3D.
Registration · CT & TA together
See their opposing actions together.
They are antagonists in their effects on fold length. They can also contract at the same time. Follow the arrows, then compare the resulting shape with the dashed outline.
The stretcher · Cricothyroid (CT)
CT contracts on the outside of the laryngeal cartilages. The thyroid tilts relative to the cricoid, tending to lengthen the folds.
Hear it: more CT usually goes with higher pitch and a lighter, “head” quality.
The thickener · Thyroarytenoid (TA)
TA contracts inside the folds. The fold body tends to shorten, thicken, and become actively stiffer.
Hear it: more TA usually goes with a fuller, “chest” quality.
Feel CT work: rest a fingertip lightly on your Adam’s apple, then slide it just below, into the small dip between the thyroid and cricoid cartilages. Glide slowly up in pitch on “ng”. Many people feel the dip narrow as CT tilts the thyroid toward the cricoid. Touch gently; never press on your throat.
The cricoid ring and the arytenoid on its back plate stay still. CT shortens on the outside and tilts the thyroid, carrying the fold’s front attachment forward. TA shortens inside the fold and draws the arytenoid slightly forward.
Same folds, same fixed back. CT moves the front attachment forward, so the folds lengthen and thin. TA shortens the folds and makes their body wider and deeper.
Exaggerated teaching geometry, not a force calculation. Arrows show direction, not measured force. This is muscle action, not rapid vocal-fold vibration.
Where do chest voice and head voice fit?
Chest-like coordination
Often involves more TA contribution and a fuller vibrating body. It is a coordination, not TA working alone.
Head-like coordination
CT helps with lengthening for higher pitches. A lighter edge pattern can accompany head-like sounds, while TA still participates.
More than two switches
“Head voice” and “mix” mean different things across teaching traditions. Head voice is not always falsetto. Pitch, closure, airflow, tissue behavior, and resonance work together.
Antagonist describes an opposing action, not a rule that one muscle switches off. CT and TA coordinate with other laryngeal muscles; they are not direct chest/head switches.
How this model works & sources
These are simplified, exaggerated diagrams. Shapes and slider positions are teaching choices, not measured anatomy, muscle activation, or a prediction of anyone’s sound. No personal information is collected by these studies.
The balance control follows one chosen example: CT increases as TA decreases, with both staying active. This is not a rule that a singer’s muscles follow an exact inverse ratio. “Increase both” demonstrates coactivation. Separate controls let you explore other combinations. Settings change qualitative geometry; they do not calculate forces, register, or pitch.
The opening between the folds is held as a viewing space; thickness does not stand in for closure. The cutaway reveals the body under the cover. CT-driven stretch and TA’s active body stiffness are different effects, so the model does not combine them into a single stiffness score.
- The Voice Foundation · The Voice MechanismMuscle attachments and characteristic laryngeal actions.
- Kochis-Jennings et al. · Muscle activity across sung registersIn seven female singers, CT activity was more related to pitch; TA and adduction varied with register quality at the same pitch.
- Herbst et al. · Glottal configurations in singingFold thickening and arytenoid closure are distinct dimensions of coordination.
- Chhetri, Neubauer & Berry · Neuromuscular control of vocal-fold postureGraded stimulation in a canine model demonstrated opposing CT and TA effects on vocal-fold strain. This supports the mechanical relationship; it does not prescribe a human singer’s muscle balance.
