The vocal ligament is the medial edge of the vocalis muscle. During a strong inspiration, the vocal folds are pulled farther apart to widen the opening into the trachea. During swallowing, the vocal folds are pulled together to protect the trachea. During phonation, the vocal folds are pulled together and airflow causes them to vibrate and make a sound; the pitch of this sound can be changed by varying the tension on the vocal ligaments.