Home / MIDI Loupe / How to & FAQ
Connect your devices, read every message, save the log, and send or route MIDI when you need to test a setup.
On a Mac, open the DMG from the download page and move MIDI Loupe to Applications. The app and the disk image are signed and notarized. It needs macOS 12 Monterey or later and runs on Apple silicon and Intel.
The Mac App Store listing stays available. Until Apple approves 2.0.0, that listing is still version 1.6. Macs older than macOS 12 keep 1.6.
On Linux, unzip the build and run ./midiloupe. ./install.sh adds a menu entry. The build needs a 64-bit system with glibc 2.39 or later, ALSA (libasound2) and GTK 3.
Open Devices. Inputs that are already present show as connected when Connect inputs automatically is on. A new input is monitored as soon as it appears.
Outputs stay off until you connect them. Turn on Connect outputs automatically only when you want every new output to be a send target.
If a keyboard or an interface is missing, plug it in and press Refresh. Create Loopback adds a virtual pair so one app can send into MIDI Loupe on the same computer.
Open Monitor. Every row is one message: time, sequence number, channel, type, source, destination, and a readable detail such as CC 7 Volume = 100 or C4 (60) · vel 90.
Rows are colored by message type — Note On, Note Off, Control Change, Pitch Bend, Clock, SysEx — not by which device sent them. Source and destination are their own columns, so several devices can share one list.
Live shows the notes you are holding, controller meters, a histogram, and the MIDI clock tempo in BPM. Freeze pauses the list so you can read it. Panic sends Note Off for the notes MIDI Loupe still considers active. Clear empties the list.
Use Filter to keep a channel, a message type, a source, or a destination. The search field matches the readable text or hex bytes, for example 90 3c. Cmd+F (Ctrl+F on Linux) moves the cursor there.
The save button stores the list as a MIDI Loupe log (.midilog) or as a CSV table. Open brings a saved log back; Back to live returns to the incoming stream. Logs written by version 1.6 cannot be opened in 2.0.0.
Click a row. The detail shows the full hex dump. Copy the event, copy the hex, or, for a SysEx message, save it as a .syx file. Cmd+C (Ctrl+C) copies the selected event.
Open Sender, choose the output and the channel, then send a note, a program change, any controller, pitch bend, or SysEx. A SysEx message starts with F0 and ends with F7. The field starts with an identity request.
Keyboard is a playable keyboard. With the computer keyboard on, the letter keys A–P play, and comma and period shift the octave. On a Mac the keyboard can sit in its own window and stay on top.
On macOS and Linux, Publish “MIDI Loupe” as a MIDI source makes other apps see an input named MIDI Loupe.
Simple mode hides Sender and Routing. Open Settings with Cmd+, (Ctrl+,), choose UI mode, and switch to Advanced.
Open Routing, pick a source and a target, and press Add. Everything that arrives at the source is forwarded to the target. A route that would loop is blocked. Each route has its own switch, so you can turn one off without deleting it.
Command on a Mac, Ctrl on Linux.
| 1 – 4 | Switch section |
|---|---|
| O / S | Open a log, save a log. Shift with S exports CSV. |
| K | Clear the monitor |
| F | Search |
| C | Copy the selected event |
| , | Settings |
The store listing is still version 1.6 until Apple approves 2.0.0. The direct download on this site is 2.0.0. Macs that cannot run macOS 12 stay on 1.6.
Not in this release. The Windows row on the download page stays empty until a file is published. On Windows a MIDI device can usually be opened by only one app at a time, and virtual ports need a loopback driver such as loopMIDI.
Connect it, then press Refresh on the Devices page. On Linux, “No access to MIDI” means your user cannot open the ALSA sequencer. Run sudo usermod -aG audio $USER, log out, and log in again. If Linux reports that no ALSA sequencer was found, load it with sudo modprobe snd-seq.
Note 60 is middle C, and programs disagree on its name. In Settings, under MIDI display, choose C3 (Logic, Ableton, Cubase, Yamaha) or C4 (Roland, scientific). Program numbers can run 1–128 or 0–127 in the same place.
Logs from version 1.6 use a different file. 2.0.0 opens logs it saved itself, as .midilog, and it can export the current list as CSV.
No. The app runs on your computer and does not collect or send personal data. The privacy policy covers the site and the Mac App Store apps.
Simple mode shows Devices, Monitor, and Keyboard only. In Settings, set UI mode to Advanced. The same window chooses the language, light or dark mode, and the size of the interface. MIDI Loupe has 11 languages.
Something still stuck? Write to g.flossmann@gfapps.com.