This 121 page PDF book provides all the required information for the MIDI Instrument Digital Interface (MIDI), the Arduino Microcontroller source code and the inter-connecting hardware.
This 259 page PDF book contains designs for MIDI software and hardware, for MIDI Keyboard Encoders ranging in size from 25 to 88 notes.
This 123 page PDF book contains designs for MIDI software and hardware, for Organ Bass Pedal Encoders ranging in size from 13 to 32 notes.