The key and scale can be controlled using either potentiometers or switches. A flag in config.h needs to be set accordingly.

The IMU (MPU6050 accelerometer and gyroscope) is optional, but gives you velocity and detune.

A minimal build requires only the Pico, the MPR121, the speaker and an amplifier or buffer.

Circuit bom (some components won't be needed, according to your configuration):

- 4x momentary switches
- Latching power switch
- 18x LEDs - Lithium battery (ideally over 1000mAh)
- TP4056 charger module
- 100Ω resistor
- 2x 220Ω resistors
- 1K resistor
- 1.8K resistor
- 2x 250K linear potentiometers
- 10K linear potentiometer
- 100nF capacitor
- 470nF capacitor
- 220nF capacitor
- 3x 10uF electrolytic capacitors
- 1000uF electrolytic capacitor
- 4700uF electrolytic capacitor
- 10uH inductor
- HT7333 3.3V linear regulator
- PAM8403D audio amplifier
- 8Ω speaker
- 3.5mm audio jack (switched)
- Metal pushpins (to use as touch pads)