Cricothyroid m

The cricothyroid m. is the only muscle that is able to tense the vocal cords, resulting in a higher pitch of the voice.  The cricothyroid m. runs from the cricoid cartilage to the thyroid cartilage, and when it contacts it causes the superior part of the thyroid cartilage (the anterior attachment of the vocal cords) to rotate forward, thus putting them in tension.  The muscle is innervated by the external laryngeal branch of the vagus n.