A controller appears to do nothing
Select its CoreMIDI input and see the arriving messages. Separate a missing signal from a mapping or application problem.
All software
MIDI utility · Free for noncommercial use
CLR MIDI Monitor
See what your MIDI connections are actually sending.
The problem
What it solves
When a controller, application or hardware connection behaves unexpectedly, the first question is whether the right message reaches the right port. CLR MIDI Monitor makes that MIDI activity visible without sending or echoing MIDI.
Too many messages to follow
Keep the latest event visible, search history and filter the display so notes, controllers and other useful details stand out.
An issue that needs a record
Inspect individual message fields and export retained events as JSON for later review. Display filters do not remove events from that export.
Follow the MIDI path
See ports, not guesses about apps
Monitor incoming CoreMIDI ports, observe events sent to selected output destinations, or enable Receive from software to receive directly from a music app.
Output rows identify the destination port—not the application sending to it. MIDI that stays inside a DAW or plug-in may not appear on CoreMIDI ports. The app does not send, echo or thru MIDI.
CoreMIDI inputs→CLR MIDI Monitor←Output destinations
Compatibility and limits
A focused CoreMIDI utility
The bundled output observer is prepared automatically. Its first setup may ask you to restart your Mac once; the app will not force a CoreMIDI restart.
- Price and license
- Free for noncommercial use · PolyForm Noncommercial 1.0.0
- Version
- 1.0.2
- Platform
- macOS 13 or later
- Processor
- Apple Silicon · no Intel or Windows build
- Capture
- CoreMIDI inputs, output destinations and direct software reception
- History and export
- Up to 10,000 retained events · JSON
- Not included
- No MIDI send, echo or thru; no MIDI 2.0 semantic decoding or complete SysEx reassembly
- Commercial use
- Requires separate permission from CLR
This is source-available software, not OSI-approved open source. The current Mac build is not signed with a CLR Apple Developer ID and is not notarized; macOS may warn or block it. See the install and security instructions above before opening it.
Read the CLR MIDI Monitor quick guide →Documentation
Manuals and quick starts
The quick guide covers port selection, direct software reception, output observation, filters, JSON export and macOS installation. The full offline manual is included in the app’s Help menu. Review the noncommercial license before using the app in paid work.
Install and macOS security instructions
- Download the app from CLR’s official release page, unzip it, and move CLR MIDI Monitor.app to Applications.
- Open it once from Applications. If macOS says it cannot verify the developer or blocks the app, close the alert.
- Only if you trust this CLR download, open System Settings → Privacy & Security, scroll to Security, choose Open Anyway for CLR MIDI Monitor, then confirm the next prompt.
- Open the app again. Do not disable Gatekeeper globally or use this exception for files from other sources.
macOS may show the warning again after an update. The app is not notarized, so this is a manual, per-app approval—not a claim that Apple has verified the build. See Apple’s instructions for safely opening Mac apps.
CLR MIDI Monitor · Version 1.0.2
Make the MIDI path visible
Free for noncommercial use on Apple Silicon Macs running macOS 13 or later.