MIDI notes keep sounding after a controller disconnects

You unplug a MIDI keyboard, lose its Bluetooth connection, or the controller disappears during a performance, but a note keeps playing. This can happen because the receiving instrument never got the message that the key was released.

Use the MIDI Test to inspect what your controller sends when you press and release keys. It can help you tell whether the problem starts at the controller or in the app or instrument making the sound.

Check what the controller sends

1. Open the MIDI Test in a browser that supports it. MIDI Test does not work in Safari. Allow MIDI access if the browser asks, then choose your controller if the page offers an input list.
2. Press and release one key while watching the message list. You should see a message for the key press and a matching release message. Some devices send a Note On message with velocity 0 to represent a release.
3. Repeat with a different key, then try the sustain pedal if you use one. Note whether the pedal sends a change when you press it and when you release it.
4. If you can reproduce the problem safely, hold one key, disconnect the controller, and look at the last messages received. Do not turn up your speakers to make the note easier to hear.

The MIDI Test checks incoming controller messages. It does not play your instrument or clear a note that is already stuck in a separate music app or hardware synth. To hear the instrument, test it in the app or device where the sound occurs.

What the result means

A key press and release both appear

The controller is sending the basic messages while connected. If the sound continues anyway, the receiving instrument may not be handling the release correctly, or a sustain pedal or app setting may be keeping the note active. Check the instrument and its MIDI input before blaming the keyboard.

The press appears but the release does not

The controller, its connection, or a setting may be preventing the release message. If this happens with one key only, that key may have an intermittent switch. If it happens with several keys, check for a stuck sustain pedal, a controller setting, or an unstable USB or Bluetooth connection.

The last message is a key press when the controller disconnects

This is a useful clue, but it does not prove the controller is faulty. A disconnect can prevent the release message from reaching the instrument. The instrument may keep the note active until it receives a reset, a release message, or its own stop command.

The key release appears, but the sound continues

The controller did report a release. The sound may be a long sample or instrument release, or the app may be sustaining the note for another reason. Check whether the sustain pedal is down, whether another controller is sending messages, and whether the same note stays active in a different instrument.

How to fix it

1. Release the keys and pedal. Let go of every key and release the sustain pedal. A pedal that is physically stuck or incorrectly detected can hold many notes even after you release the keys.
2. Stop the stuck sound in the instrument. Use the instrument or music app's panic, reset, or stop-all-notes control if it has one. The exact name varies. If the sound is coming from a hardware synth, use its own controls or restart it only after you have saved any work.
3. Reconnect the controller. Unplug and reconnect a USB controller, preferably directly to the computer rather than through a hub. For Bluetooth, reconnect from Settings › Bluetooth & devices › Devices in Windows 11 or System Settings › Bluetooth on macOS.
4. Check the instrument's MIDI input. In the app or synth, make sure the correct controller is selected and that it is listening on the channel the controller uses. If the problem happens only in one app, update or reset that app's MIDI input settings before changing the controller.
5. Check sustain pedal behavior. Disconnect the pedal and test a few keys again. If the notes stop sticking, reconnect the pedal and check its polarity or calibration setting in the controller or instrument. A pedal can behave as pressed when it is released if its polarity is set incorrectly.
6. Close other MIDI apps and retest. Another app may be receiving or routing the controller's messages. Close music software, virtual instruments, and MIDI routing tools, then test the controller again. If the problem began after sleep or a reconnect, restart the affected app and reconnect the controller.

When the controller may be faulty

Test the controller by itself in MIDI Test, then try another USB port or a different computer if available. Press and release the same keys several times. If a particular key repeatedly sends a press without a release while the controller remains connected, that key or its internal contact may be failing. If all keys stop reporting releases only when the cable moves, suspect the cable or port.

If the messages look normal in the test but a particular instrument keeps notes sounding, the controller is less likely to be the cause. Check that instrument's settings or contact its support. For a controller that fails on more than one computer, check its warranty or ask a repair shop about the keyboard or connection.

Why a disconnect can leave a note active

MIDI sends separate messages for pressing a key and releasing it. A receiving instrument starts a note when it gets the press message, then stops or fades it when it gets the release. If the connection drops between those events, the receiver may not know the key is no longer held. The instrument can keep the note active even though the controller is unplugged.

A browser test can show messages that reach the browser, but it cannot inspect the internal state of another music app or hardware synth. Use it to check the controller's incoming messages, then clear the sound at the device that is producing it.