Ventricular folds or “false folds”, situated just above the vocal folds. A type of vocal disorder called hyper-ventricular phonation is associated with abnormal muscle patterns resulting from hyper-activity in the false fold region. Either the false folds are adducted more than the true folds or they adduct with the true folds to create a complicated vibration pattern. Some performers and cultures use this type of phonation for special effects.
Titze, Ingo, “Principles of Voice Production”, 1st Ed., Prentice Hall, ppg.321-322.