Abductor of the larynx is:

Abduction (opening) of the vocal folds: The posterior cricoarytenoid muscles pull the muscular processes posteriorly, rotating the vocal processes laterally and thus widening the rims glottides. Adduction (closing) of the vocal folds : The lateral cricoarytenoid muscles pull the muscular processes anteriorly, rotating the arytenoids so their vocal processes swing medially. When this action is combined with that of the transverse arytenoid muscles, which pull the arytenoid cailages together, the gap between the vocal folds is decreased. Air pushed through the rima glottidis causes vibration of the vocal ligaments.