There are two controllers that can be attached to both of your thighs (or share one with a partner), giving you the option to move around or dance while you play. The sensor pads can be slapped like an electronic drum kit, with the volume varying according to the strength of the slap. The Kneeslapper inputs midi data to a midi synthesizer or audio recording program like Garageband. You can choose a different instrument sound for each of the sensor pads.