Abstract
This case study describes one-year treatment of a 30-year-old man with the autism spectrum disorder (ASD), with almost undeveloped speech. The improvement was achieved after weeksly one-hour music therapy sessions with an improvisational approach. The program of individual sessions is described in several phases and understood as a therapeutic process supervised by a mentor. A series of musical interventions and interaction in the form of a musical dialogue between the patient and the therapist had a beneficial influence on communication, undesired behaviour, and complete functioning of the patient.