DMGARP is written in RGBDS assembly, tuned for live performance. It runs as a
self-contained 32 KB ROM on real hardware or any accurate emulator.
Four sound channels, ten pages of live-editable parameters, 28 scale banks
spanning church modes, harmonic-minor modes, Messiaen modes, and Ethiopian
pentatonic scales. All parameters take effect immediately — no menus to commit.

Aleksi Eeben, the author of GB Electric Drum, once answered my request for source
code with "It's a good practice. Go program it yourself." With DMGARP I finally did it.

Download the ROM of the current version from Github

The repo is located at https://github.com/kennhartwig/dmgarp