| name | reaper-jsfx-midi |
| description | MIDI processing patterns for JSFX plugins. Use when building MIDI utilities, arpeggiators, chord generators, note filters, or CC processors. Triggers on requests for MIDI effects, arpeggiator, chord, transpose, or MIDI routing in JSFX. |
| disable-model-invocation | true |
| license | MIT |
| metadata | {"author":"mthines","author_name":"Mads Thines Coello","author_email":"madsthines@gmail.com","version":"1.0.0","workflow_type":"implementation","tags":["jsfx","reaper","midi","arpeggiator","chord"]} |
REAPER JSFX MIDI Processing
Patterns for MIDI utility plugins including note processing, arpeggiators, chord generators, and CC manipulation.
Requires: reaper-jsfx-core for language fundamentals.
Rules
| Rule | Description |
|---|
| midi-basics | MIDI message structure, receive/send, SysEx handling |
| midi-transform | Note transposition, velocity scaling, CC mapping |
| midi-generate | Arpeggiators, sequencers, chord generators |
| midi-routing | Multi-bus routing, channel filtering, splitting |
Official Documentation
Key Principles
1. MIDI-Only Plugin Structure
desc:MIDI Utility
tags:midi
in_pin:none
out_pin:none
@block
while(midirecv(offset, msg1, msg2, msg3)) (
// Process and forward
midisend(offset, msg1, msg2, msg3);
);
2. Always Forward or Handle All Messages
@block
while(midirecv(offset, msg1, msg2, msg3)) (
status = msg1 & $xF0;
status == $x90 || status == $x80 ? (
// Process notes
process_note(offset, msg1, msg2, msg3);
) : (
// Pass through everything else unchanged
midisend(offset, msg1, msg2, msg3);
);
);
3. Preserve Timing
@block
// Use original offset for timing-critical events
while(midirecv(offset, msg1, msg2, msg3)) (
// Transform but keep original offset
midisend(offset, new_msg1, new_msg2, new_msg3);
);
Quick Reference
