The vocal apparatus consists of two pairs of mucosal folds. These folds are false vocal folds (vestibular folds) and true vocal folds (folds). The false vocal folds are covered by respiratory epithelium, while the true vocal folds are covered by stratified squamous epithelium. The false vocal folds are not responsible for sound production, but rather for resonance. The exceptions to this are found in Tibetan Chant and Kargyraa, a style of Tuvan throat singing. Both make use of the false vocal folds to create an undertone. These false vocal folds do not contain muscle, while the true vocal folds do have skeletal muscle.