MIDI clock drift before an audition: fixes

Your virtual instrument starts in time, then seems to slip ahead of or behind the beat during an audition. The cause could be a clock source, a routing loop, dropped MIDI messages, or audio latency. These problems can sound similar, but the right fix depends on which one is happening.

Start by checking that your controller is reaching the computer. The MIDI Test can show incoming notes and controller messages. It does not measure clock accuracy or replace a test inside your instrument software, so use it to narrow down where the problem begins. The test does not work in Safari.

Check the MIDI input and audition timing

1. Open the MIDI Test in Chrome or Edge on a computer. Choose your MIDI keyboard or controller from the device list, and allow access if the browser asks.
2. Press several keys, then move a knob or pedal if you use one. Confirm that the test receives messages for each action. This checks the input connection, not the timing of the virtual instrument's sound.
3. If your controller or another connected device sends MIDI clock, start its clock source and watch for incoming clock activity in the message view. The test can help reveal whether messages arrive or stop, but it does not calculate drift or provide a precise timing measurement.
4. Open your virtual instrument setup and play a short, steady pattern against its metronome. Record or listen to the start and end of the same passage. Note whether the timing is already offset at the beginning or gradually moves farther out.
5. Repeat the audition after changing only one thing, such as the clock source or USB connection. That makes it easier to identify which change helps.

If your controller does not send MIDI clock, the browser test cannot check its clock timing. Use the test to verify notes and controls, then diagnose the clock and audio path in the software used for the audition.

What the result means

Notes or controls do not appear in the test

The computer is not receiving those messages from the selected device. Check the selected input, cable, connection, and browser permission before adjusting the virtual instrument. If notes appear only after reconnecting, the device or USB path may be unreliable.

Messages appear, but the audition drifts over time

The controller is communicating, but that alone does not prove its clock is stable. Check which device is the timing master, whether the instrument is set to follow the right clock, and whether a second clock source is also running.

The timing is off by the same amount from start to finish

A steady offset is more likely to be latency than clock drift. Audio buffer size, instrument processing, and the monitoring path can delay what you hear without changing the tempo over time.

The timing starts well and gets worse gradually

That pattern points more toward a clock mismatch or unstable synchronization. A tempo mismatch between the software and an external clock can cause the gap to grow as the passage continues.

How to fix it

1. Choose one clock master. Decide whether the computer software or an external device supplies the clock. Set the other device to follow that source. Two devices trying to lead can produce unstable timing or confusing tempo changes.
2. Match the tempo and sync mode. Check the project tempo and the controller's tempo if it has one. If the software should follow external clock, select that mode; if the computer should lead, set the controller to follow the computer. Menu names vary by instrument software.
3. Remove duplicate MIDI routes. Check that the same controller is not reaching the instrument through two inputs or a feedback loop. If you do not need MIDI thru or soft thru, turn it off for the audition. A duplicate route can make notes sound doubled or uneven.
4. Connect the controller directly. Temporarily remove a USB hub, adapter, or extension and connect the controller to another computer port. Try a known-good cable, and avoid loose connectors. If you need a hub, use a powered hub with a stable connection.
5. Reduce competing work. Close unnecessary applications and browser tabs, then repeat the same passage. On Windows 11, check Settings › System › Power & battery › Power mode. On a Mac laptop, check System Settings › Battery › Low Power Mode. Compare results while plugged in and on battery, but change one condition at a time.
6. Check the audio path separately. If MIDI messages arrive but the sound is late, review the audio buffer and output device in your instrument software. A smaller buffer can reduce monitoring delay, but it may cause clicks or dropouts if the computer cannot keep up. MIDI clock and audio buffer size affect different parts of the setup.
7. Restart and update only after simpler checks. Close the instrument software, reconnect the controller, and reopen the project. If the issue persists across sessions, check for an available controller firmware or driver update and repeat the test with the same cable and settings.

When it may be the hardware

Suspect a cable, port, or controller only after testing with one direct USB connection and checking the setup in more than one compatible application. If notes or clock messages repeatedly stop when the cable moves, try a different cable and port first. If the same device still drops messages on another computer, contact the manufacturer or arrange a repair. Do not replace a controller based on one audition, since sync and audio settings can create similar symptoms.

Clock drift is not the same as monitoring delay

MIDI clock tells compatible devices how fast to follow a musical tempo. Monitoring delay is the time between playing a key and hearing the sound. A delay that stays roughly constant is different from a beat that gradually slides out of time. For more on checking incoming clock messages, see How to test MIDI clock messages for a loop.

Keep the test pattern, tempo, instrument, and connection the same while comparing changes, so you can tell whether the timing actually improved.