This paper presents a system to control the playback of audio files by means of the standard classical conducting technique. Computer vision techniques are developed to track a conductor's baton, and the gesture is subsequently analysed. Audio parameters are extracted from the sound-file and are further processed for audio beat tracking. The sound-file playback speed is adjusted in order to bring the audio beat points into alignment with the gesture beat points. The complete system forms all parts necessary to simulate an orchestra reacting to a conductor 's baton.