This article proposes a wireless handheld multimedia digital instrument, which allows one to compose and perform digital music for films in real-time. Not only does it allow the performer and the audience to follow the film images in question, but also the relationship between the gestures performed and the sound generated. Furthermore, it allows one to have an effective control over the sound, and consequently achieve great musical expression. In addition, a method for calibrating the multimedia digital instrument, devised to overcome the lack of a reliable reference point of the accelerometer and a process to obtain a video score are presented. This instrument has been used in a number of concerts (Portugal and Brazil) so as to test its robustness.