SigmaTizm is a virtual additive synthesizer instrument designed for live play. It can be controlled via the computer keyboard or with an external MIDI device and can also be used to control external MIDI devices. SigmaTizm featues 128 harmonic oscillators and detailed editing of sound parameters such as attack and release harmonics, vibrato, and volume envelope. Harmonics can be changed in real-time for interesting sound textures and filtering effects.