The thyroarytenoideus muscle is a muscle within the larynx which extends from the back of the thyroid cartilage to the front side of the arytenoid cartilage. When it contracts, it pulls the arytenoid cartilage forward, thus loosening the vocal folds. The deep upper part of this muscle is known as the vocalis muscle. This muscle can change the tenseness of small segments of the vocal folds in order to vary tonal qualities of the voice.