[Unusual causes of biphonation].

Biphonation or diplophonia can be caused by several mechanisms. Although helpful for communication in some animals, biphonation in humans is usually perceived as increased roughness. Herein we report two unusual causes for biphonation. In the first case, a woman suffered from vocal fold bamboo nodes. These decoupled the anterior from the posterior part of the vocal folds, leading to an intermittent anterior-posterior vibration pattern during phonation. In the second case, a patient underwent a pitch-raising operation. Postoperatively we saw a transversal fixation of the vocal fold mucosa caused by a suture. This fixation led to two separated "neo" glottides, one being in the anterior third and the other in the posterior third of the vocal folds.