3 The larynx viewed from the rear: the little arytenoid cartilages each socketed to the cricoid cartilage (some of the muscles which govern their po-stion are not shown here). With the vocal cords together (a), air cannot pass through the larynx because there is tissue betweeen each of the of the vocal cords and the inner surface of the thyroid cartilage. A valve is thus formed , whicgh opens and closes at the pitch frequency of the note being sounded, just as a trumpet players lips do. When the breathe, the valve is relaxed and open (b). In singing or speaking, the amount of tension in the vocal cords is affected by muscles attached to the rear of the arythenoid cartilages, and also by the degree to which the front of the thyroid cartilage is tipped down by muscles outside the larynx