JackTopGuitar is a digital musical interface (DMI) that uses an electric guitar, microphone and foot pedal for a computer-based audio-visual live performance. It consists of voice commands, voice gestures, guitar gestures, pedal controls, and their combined actions. The performer can project videos and control various parameters of sequencers and effectors. The interface realizes real-time audio-visual musical performances. JackTopGuitar is based on the traditional electric guitar playing style, and its performing expression is augmented by the extra functions such as speech recognition. Visual expressions are not just visualization of vocal and guitar plays but a part of the performance created by the music and performer’s control.