--bind '1:20:127=open ~/Downloads' and a stomp opens the folder. It was built for the Behringer FCB1010 sitting unused under somebody’s desk, but nothing in it is FCB1010-specific — any CoreMIDI source works, and it follows hotplug. The design note is the good part: it only reads MIDI, which needs no permissions at all, and hands the doing to your shell, Hammerspoon or Keyboard Maestro, because a sandboxed app could never be given that reach. Run it bare and it prints one JSON object per line instead.