Written for an Arduino Uno with MIDI IN, OUT, and THRU.

Signals sent from a MIDI controller (e.g. a keyboard) get forwarded immediately to the device on MIDI THRU, and forwarded with a delay to the device on MIDI OUT.

The result is somewhat similar to playing with a normal audio delay pedal with a single repeat, except that the delayed signal can control an entirely separate instrument from the dry signal.

To be clear, this is not a MIDI-controlled delay pedal. There are no audio signals involved. Rather, MIDI signals get stored in a buffer for a short time before sending them onwards.

Bloopers: youtube