CDMIDItestCircuit Drift Labs
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MIDI DIAGNOSTIC BENCH

Inspect the signal, not the guess.

Run a guided controller check, inspect raw MIDI, isolate suspicious controls, compare baselines and export technician-friendly evidence.

Ready

Enable MIDI and select an input, or use the monitor directly.

Checklist

Pass/fail sheet for the selected preset. Updates live as you test.

Findings

Measured observations that may deserve attention.

Observed inventory

Live MIDI Monitor

Decoded events and raw bytes. Capture remains local.

TimeDeviceChTypeMessageValueDecimalHex

Message statistics

Channel activity

Record & replay

Record a session to a file, or load one to analyse without the hardware. Replay runs the same tests.

MIDI 2.0 / UMP decoder

Browsers only see the MIDI 1.0 translation of MIDI 2.0 devices. Paste 32-bit UMP words (hex) from a UMP capture to decode them.

SysEx inspector

Requires the separate SysEx permission. Shows length, manufacturer ID bytes and hex; payloads are not interpreted.

Detected controls

Select a CC to inspect.

Control detail

No control selected.

Pedals & expression

Aftertouch

High resolution / parameters

Pitch bend

Range centered on neutral (0). Release the wheel several times to measure center return.

MPE-like activity

Per-channel note, pitch bend, pressure and CC74. Passive observation only; not an MPE conformance check.

Keybed

No notes observed.

Held notes / chord

Velocity diagnostics

Per-key velocity

MIDI clock

Performance timing

Traffic anomalies

Loopback test

Physically or virtually route selected MIDI OUT back to selected MIDI IN.

Round-trip latency

Browser-to-MIDI-loopback round trip. This is not DAW/driver latency.

MIDI Output Tester

Connection log


  

  
SysEx tools
Requires Enable SysEx. SysEx can overwrite device memory: only send data you understand.

    

    
    

  
Clock generator & sync test
Sends MIDI clock from the selected output. With the output looped to the input the app measures tempo error, drift and jitter.

  
Path comparison (second input)
Compare the selected input (A) with a second input (B), for example a controller versus an audio interface, to see where messages are lost.






  

    
MIDI Learn
Waiting for a message…

    
Mapping worksheet
MessageLabel

  






  
Charts
Pick a chart. Data comes from the live or replayed capture.






  

    
Advanced Diagnostic Tests
Ten analyses of the live capture. Play or operate the controller as each card describes; every card explains what its result means. Results are measurements and triage hints, not repair diagnoses.

    

    
The burst test needs a MIDI output looped back into the selected input.

  

  
Active tests (send & verify)
Sends known MIDI from the selected output and checks what returns on the selected input. Route OUT back to IN (cable or virtual loopback). Do not run into a synth you do not want to hear.

  






  

    
Windows MIDI & USB logs
Reads the Windows Event Log, Device Manager state, services, power settings, setupapi and crash reports for MIDI/USB problems and explains each one. The scan is read-only. It runs automatically after tests in the Windows desktop app.

      

    

  

  






  

    
Diagnostic Report
Evidence-focused summary, baseline comparison and exports.

    

    

    

    
Raw report JSON

  





Related Circuit Drift Labs tools
TrackStatsTransposition CalculatorLoudnessBatch
Experiments
Binaural Web BeatsBabbleForge





MIDItest Help
Getting started
Use a Chromium-based browser on a secure page. Enable MIDI, choose an input, then use Quick Test or Monitor.
SysEx
System Exclusive access is requested separately because browsers require an additional permission. MIDItest only displays observed bytes and does not interpret proprietary payloads.
Guided test steps
  1. Connection — enable MIDI and pick the input.
  2. Key sweep — press every key or pad once. Set an expected range on the Keyboard tab to list unseen keys.
  3. Velocity — play soft to hard, then strike one key repeatedly at similar force.
  4. Controls — move every knob/slider end to end, then leave it still for a moment.
  5. Pitch bend — push fully both ways and let it spring back several times.
  6. Mod / expression — sweep the mod wheel and expression controls.
  7. Buttons — press each button once.
  8. Pedals — press sustain and move expression pedals.
  9. Aftertouch — press into held keys if supported.
  10. Timing / loopback — optional, see below.
  11. Review — read findings, label mappings, save a baseline, export.
Skip marks a step as untested rather than failed. End stops the guided run and keeps the data.
What the measurements mean
Range / coverage: lowest and highest values seen, as a percentage of 0–127. Jitter: average size of back-and-forth value flicker while a control is moved little or not at all; a smooth sweep shows zero. Jumps: steps larger than 12 between consecutive values. Reversals: direction changes. Dead zones: gaps of 4+ values never reported. Bounce: a switch flipping back within 40 ms. These are measured observations and evidence for troubleshooting, not automatic hardware-failure diagnoses.
Advanced tests
The Tests tab runs ten analyses on the live capture (protocol audit, link health, double-trigger, velocity response, rollover, sweep linearity, encoder integrity, pitch-bend return, pedal polarity and a loopback burst test). Each card shows how to run it and explains what its result means.
Windows logs
In the Windows desktop app the Windows Logs tab scans the Event Log, Device Manager, services and setupapi/crash logs for MIDI and USB errors, explains each one and re-scans automatically after tests. In a browser, copy the PowerShell scan, run it on the PC and import the saved JSON (or import a setupapi.dev.log / Report.wer file).
Loopback
Connect a MIDI cable from the selected output port to the selected input port (or use a virtual loopback port such as loopMIDI on Windows), then press Run loopback. MIDItest sends a known Note/CC/Program/Pitch Bend sequence and counts matched, altered, missing and extra messages.
Latency limits
Latency is browser-to-MIDI-loopback round-trip time. It includes browser scheduling, operating-system MIDI drivers and the interface, and is not the same as DAW or audio driver latency.
Labs
Turn optional features on or off. Disabled features are hidden.
Privacy
Capture, mappings and reports stay in the browser. MIDItest contains no MIDI telemetry backend.



Glossary