(Also known as the sinus of the larynx). A crevice that sits between the false folds above and the vocal folds below. It allows the false folds to glide over the vocal folds during changes to the shape of the epiglottic funnel in singing (and sealing off of the larynx during swallowing and coughing). It is lined by mucus glands which help lubricate the vocal folds. There is an additional extension of this crevice deep into the false fold and aryepiglottic fold known as the saccule. This is also lined by mucus glands and  provides additional lubrication.