http://busycircuits.com/alm003/ The SID GUTS supports to following SID chip features via modular control; 1volt per octave control of a ‘core’ SID oscillator 0-5v input (with tunable offset) Direct and voltage control of oscillator wave shape selection (Pulse, Triangle, Square, Saw). Filter switchable between 4 modes - 12dB/Octave HP , LP , BP & Notch (HP+LP). Direct and Voltage control (with offset) of Filter cutoff and Resonance. 1 volt per octave control of second SID ‘modulation’ oscillator. Direct and voltage control of modulation oscillator ‘type’; ring modulation, sync or none. Direct and voltage control of pulse wave pulse width. External audio input. Super Sache!