M-Audio Keystation 88ES 88-Key USB MIDI Keyboard Controller with Semi-Weighted Keys (OLD MODEL) 88 velocity-sensitive, semi-weighted keysPitch bend and modulation wheels Advanced function button for programming Sustain and expression pedal inputs Assignable data up/down buttons Built-in USB MIDI interfaceMIDI out jack routes MIDI signals from keyboard or computer to external devices Powered via USB or 9V DC adapter (sold separately)Mac OS X and Windows XP class compliant