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MIDI keyboard sends duplicate notes: causes and fixes

Find out whether your MIDI keyboard sends each note twice or your music app is duplicating it, then check the most common causes.

Ryan MitchellHardware tests Tests 4 min read

You press a key once, but hear two notes, a stutter, or a note that keeps playing. The cause could be the keyboard, a MIDI connection, or a setting in your music app.

First, check what the keyboard sends before the signal reaches your music app. The MIDI Test shows incoming messages from a MIDI keyboard or controller, which helps separate a keyboard problem from an app or routing problem.

Check what the keyboard sends

  1. Open the MIDI Test on a computer and connect your keyboard. If your browser asks for MIDI access, allow it. The test does not work in Safari, so use another supported browser. See why browser MIDI testing does not work in Safari.
  2. Find your keyboard's messages in the test. If more than one MIDI device is connected, unplug the others and check again.
  3. Press one key once, then release it. Leave a short pause before pressing it again. Repeat with a few keys, including one at the low and high ends of the keyboard.
  4. Compare the messages with what you hear in your music app. Check whether the test shows repeated note events, or whether the sound only repeats after the signal reaches the app.

What the result means

One press produces repeated note events in the test

The duplicate is already present before your music app processes the input. A worn or dirty key contact, a keyboard setting, or a device between the keyboard and computer may be sending repeated events. If it happens only on one key, the key mechanism is a stronger suspect.

The test shows one event, but the app plays two notes

The keyboard is probably sending a single press correctly. Look for duplicate input routing, MIDI echo, or multiple tracks and instruments listening to the same keyboard. A layered instrument can also sound like two notes even when it receives only one MIDI event.

The note starts once but keeps playing

The keyboard or connection may be failing to send the note-off event when you release the key. A missed note-off can leave a note stuck. Sustain pedal input, a loose cable, or a problem in the music app can also make a note continue.

It happens only with certain keys or when you press quickly

A key contact may be bouncing, which means one physical press is registering several times. If fast playing is the only trigger, also check whether the keyboard has an arpeggiator, sequencer, or repeated-note feature enabled.

How to fix it

  1. Check whether one key is the trigger. Test several keys with slow, separate presses. If only one key sends duplicates, check whether anything is physically stuck around it. Do not spray cleaner into the keyboard.
  2. Turn off repeated-note features. Check the keyboard for an arpeggiator, sequencer, split, layer, or MIDI merge setting. These features can send or play more than one note from a single key press. Use the keyboard's manual if the setting names are unclear.
  3. Remove extra MIDI inputs. Disconnect other keyboards, controllers, and MIDI adapters, then test again. In your music app, make sure the same keyboard is not selected through two input ports or routed to two tracks that both play a sound.
  4. Check MIDI echo or soft thru. A music app can send incoming MIDI back out through another device or virtual port, creating a loop. Turn off MIDI echo or soft thru temporarily, and avoid routing the same input back to itself. Menu names differ between apps.
  5. Reconnect the keyboard directly. Try another USB port and cable, and bypass a hub or adapter if possible. For a Bluetooth MIDI controller on Windows 11, check Settings › Bluetooth & devices › Devices. On a Mac, open Applications › Utilities › Audio MIDI Setup, then choose Window › Show MIDI Studio to check whether the device appears.
  6. Restart the app and computer. Close the music app completely, disconnect the keyboard, restart the computer, then reconnect the keyboard and test before opening other MIDI software.
  7. Check for a keyboard update or repair. If repeated events still appear in the MIDI Test when the keyboard is connected directly, check the manufacturer's instructions for a firmware update. If only particular keys keep sending duplicates, the key contacts may need service.

When the keyboard may be faulty

Try the keyboard on another computer with the MIDI Test, using a different cable if it connects by USB. If the same key sends repeated events on both computers, and the problem remains with other MIDI devices disconnected, the keyboard is the likely source. A recently purchased keyboard may be covered by warranty. For an older instrument, compare the repair cost with replacing it.

Why two MIDI messages do not always mean two sounds

MIDI carries note instructions, not audio. A note-on message tells an instrument to start a note, and a note-off message tells it to stop. Some MIDI devices represent note-off as a note-on message with velocity zero, so the event label alone may not tell you that a note was repeated.

Two overlapping note-on messages for the same pitch can also behave differently across instruments. One sound may retrigger, two sounds may layer, or a note may seem to hang if a matching note-off is missed. Compare the messages in the test with the sound in your app to find where the behavior begins.

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