The Hotone Bass Press is a 3-in-1 compact pedal designed for bass players. This unit features wah, volume, and expression modes. The wah mode is specially optimized for bass frequencies, featuring wild, strong, clear sound character without affecting your bottom end. If musicians the world over agree on one thing, it is their common hatred of the volume sucking quality of passive volume pedals. Bass Press' volume mode is an active volume design, which keeps your tone pristine. Fine tune the bottom end with the volume range control. Expression pedal mode can be used without a battery or external power supply. It is compatible with most digital effects and connects with a standard stereo 1/4 inch. jack. This mode also suports keyboards and other instruments that use expression control.