Mini MIDI Box is a customizable, open source Arduino based MIDI controller.

With 2 MIDI outs, a MIDI in, and a UI, create any kind of midi controller you'd like, be that a sequencer, arpeggiator, or anything else!

Current firmware consists of a basic 2-track sequencer. More firmware types to come.

Visit the Git repository for BOM, build information, firmware, etc:
https://gitlab.com/WormyMaple/mini-midi-box