Critter & Guitari Pocket Piano The Pocket Piano is a mini electronic synthesizer with a big sound! The Pocket Piano is housed in a sturdy aluminum and hardwood case and also includes a built-in speaker, a 1/4" output jack, and wooden keys made for a refined touch. It can be powered both by a 9V battery or a wall wart (not included). When you change modes with the right-most wooden button, a color LED above that button indicates what mode is selected with a different color for each mode. The entire keyboard may be tuned over a 2 octave range by turning the knob second from right. Volume is controlled by the right-most knob. The function of the remaining two left knobs depend on what mode is selected, and are described below. There is also a button that selects waveform (sine, square, triangle, sawtooth) in the first four modes, and shifts the keyboard an octave higher in the last two modes.