Pimoroni Piano HAT
This HAT comes with 16 touch sensitive buttons, up and down octave controls, and 13 piano keys from C to shining C! Each button on Piano HAT can be individually watched in Python and hooked up to whatever mad-cap contraption or project you can imagine.
For all you Pro's wanting to take this a step further, you can also make your Piano HAT output regular MIDI commands with a USB to MIDI adapter and take charge of your hardware synth gear.
The Piano HAT is compatible with Raspberry Pi 3, 2, B+ and A+ and comes fully assembled with a treasure trove of examples to get you started.
16 touch sensitive buttons
13 piano keys (a full octave)
Octave up/down buttons
Instrument cycle button (great for use with synthesizers)
16 LEDs (let them light automatically, or take control with Python)