Why a sustain pedal acts backward when plugged in

You press the sustain pedal and the notes stop, then lift your foot and they ring out. This usually means the keyboard is reading the pedal’s on and off states in reverse, not that the pedal is broken.

Test the MIDI signal first to see whether the reversal starts at the pedal and keyboard or happens later in your music software. The MIDI Test can show messages from your keyboard, including pedal input.

Test the pedal signal

1. Open the MIDI Test in a browser other than Safari. MIDI Test does not work in Safari.
2. Connect your keyboard or MIDI controller to the computer. If the browser asks for MIDI access, allow it.
3. Find the pedal input or message display, then press and release the pedal several times. Keep the keyboard connected directly if possible, rather than through a hub.
4. Compare the messages when the pedal is up and down. If the test shows more than one MIDI device, make sure you are checking the keyboard you are using.

This test checks the messages your controller sends. It does not check how a particular piano sound or music app responds to those messages.

What the result means

The pedal-up and pedal-down states are reversed in the test

The keyboard is sending the reverse of the behavior you want. A pedal’s switch can be wired or interpreted as normally open or normally closed. If the pedal and keyboard expect different states, the keyboard may read a released pedal as pressed. Look for a polarity switch or a pedal polarity setting on the keyboard, or use its startup procedure to detect the pedal.

The test shows the right states, but your music app behaves backward

The pedal and keyboard are probably working. The app may be using a different MIDI input, applying a reversed control assignment, or responding to another pedal message. Check the app’s MIDI input and controller mapping before changing the pedal itself.

No pedal messages appear

The keyboard may not be sending the pedal input to the computer, or the pedal may be connected to the wrong jack. Check the connection and browser access, then try another compatible pedal if you can.

The pedal works only after reconnecting it

Some keyboards detect pedal polarity when they start. If the pedal is held down or disconnected during startup, the keyboard may choose the wrong state until you restart it.

How to fix it

1. Check the jack label. Plug the pedal into the keyboard’s jack labeled for sustain or damper. An expression or assignable pedal jack may use a different type of input, even if the plug fits.
2. Check the pedal’s polarity switch. If the pedal has a switch marked for polarity or normal and reverse, change it, then test both pedal positions again. The correct setting is the one where the pedal released means sustain off and pressed means sustain on.
3. Restart with the pedal released. Turn the keyboard off, make sure the pedal is not pressed, connect it to the correct jack, and turn the keyboard back on. Some keyboards detect the pedal’s state at startup. Check the keyboard manual for its recommended startup procedure.
4. Look for a pedal setting on the keyboard. Some models let you reverse pedal polarity or reassign a pedal in their settings. The exact menu depends on the model. Windows 11 Settings and macOS System Settings do not provide a system-wide sustain polarity switch, so look in the keyboard’s own menus or manual.
5. Check the music app’s MIDI settings. Select the correct keyboard as the MIDI input and check whether a controller assignment reverses or remaps the sustain signal. If the MIDI Test shows correct states but the app does not, focus on the app’s mapping.
6. Reconnect and test one item at a time. Try a different cable, keyboard jack, or compatible pedal. Change only one item between tests so you can tell which connection causes the reversal or missing signal.

When the pedal or keyboard may be faulty

Test the pedal with another compatible keyboard, or test a known-working pedal with yours. If your pedal sends the wrong state on multiple keyboards, its switch or cable may be faulty. If several compatible pedals act backward or fail on one keyboard, the jack or keyboard settings may be the problem. For a new product, contact the seller or manufacturer before opening the pedal or keyboard. For older equipment, a repair shop can check the jack and switch.

What the MIDI values mean

Sustain is commonly sent as MIDI Control Change 64, often written as CC64. In the usual convention, values from 0 to 63 mean off, while values from 64 to 127 mean on. A MIDI monitor may show these numbers rather than words. Compare the value with your foot up and down: if the higher value appears when the pedal is released, the controller is sending the opposite state. Some instruments also respond to other messages or have their own settings, so use the behavior you need in your music app as the final check.