It reverses the pedal’s electrical on-off interpretation. A sustain pedal polarity switch changes how the piano reads the pedal’s open and closed states, helping compatible pedals correct reversed sustain behavior.
What does a sustain pedal polarity switch do?
It reverses the pedal’s electrical on-off interpretation.
A compatible switch lets the pedal match a piano that expects the opposite resting state, correcting sustain that activates when your foot is raised.
A simple sustain pedal acts like a switch. One piano may read the resting circuit as open while another expects it closed. When those expectations differ, notes may sustain until the pedal is pressed and stop when it is released. The switch changes that relationship; it does not change the sound engine or add half-pedaling. MIDI Association explains controller messages in its USB-MIDI overview, although the physical pedal connection is defined by the piano manual.
Identify the symptom before moving the switch. A reversed pedal is different from a loose plug, damaged cable, unsupported connector or incorrect pedal mode.
How can you tell whether pedal polarity is reversed?
Test a held chord with the pedal untouched.
Reversed polarity usually makes notes continue when the pedal is up and release when it is pressed, consistently across the keyboard.
Turn the piano off, connect the pedal fully, then power on without touching it, unless the manual gives another sequence. Play a chord, release the keys and listen. Repeat while pressing the pedal. If the behavior is exactly opposite to normal sustain, polarity is a likely cause. MusicTheory.net explains note duration in its duration lesson, which can help make the listening test deliberate.
If sustain flickers, works only at certain cable positions or affects some notes inconsistently, stop treating it as a simple polarity problem and inspect compatibility or hardware.
When should you move the polarity switch?
Move it only with the piano powered off.
Disconnecting power before changing the switch gives the piano a clean startup state and avoids confusing automatic pedal detection on some instruments.
Switch the piano off, remove your foot from the pedal and move the polarity selector firmly to its other marked position. Confirm that the plug is inserted into the correct sustain or damper jack rather than an expression or audio port. USB-IF provides general connector context at USB.org, but a plug that fits does not prove electrical compatibility. Power on and repeat the same chord test.
Do not toggle the switch repeatedly while playing. Keep one known test and change only the switch position so the result identifies polarity rather than another variable.
Why can a pedal still fail after polarity is corrected?
The connector, wiring or pedal type may be incompatible.
A polarity switch cannot repair a damaged cable, wrong plug standard, unsupported continuous pedal or piano jack configured for another function.
Inspect the cable and plug for visible damage and confirm the exact pedal model against the piano documentation. A basic switch pedal and a continuous or half-damper pedal can send different information. Do not force an adapter or assume a stereo-looking plug provides the required wiring. The CPSC home safety resources support keeping cords and equipment in safe condition.
Test the pedal directly without extension cables or splitters. If the fault remains, record the piano model, pedal model and test result before contacting official support. Check whether the pedal works on another officially compatible instrument only when the documentation supports that comparison.
Can apps or MIDI settings cause reversed sustain?
They can change software response, but test hardware first.
If the piano behaves normally through its own sound but a connected app sustains incorrectly, the MIDI mapping or software instrument deserves a separate check.
First test the piano speakers with the app disconnected. Then connect one MIDI route and use a basic software sound. Sustain commonly appears as a controller message, and an app may filter, remap or interpret it differently. Apple describes app permissions in its information access guide; use equivalent official controls on other devices.
Avoid changing pedal polarity, app mapping and connection method in one attempt. A controlled sequence reveals whether the issue belongs to the pedal, piano or software path. Save the basic piano-only result before reconnecting software so you have a reliable baseline for later troubleshooting.
How should you test the pedal after setup?
Check short notes, chords and repeated pedal changes.
A complete test confirms normal release, clean repeated changes and consistent behavior across the practice setup rather than one successful held note.
Play a single note without pedal, then with pedal. Repeat with a chord and several slow press-release cycles. Listen for notes clearing when the pedal rises and sustaining only when expected. NIST describes repeatable measurement principles through its Time and Frequency Division; here the practical goal is the same test under the same conditions.
Finally test the Smart Piano App or recording setup if you use one. Keep the working switch position noted on the cable label. Test again after a brief pause and normal restart to confirm the behavior does not depend on one temporary connection state.
Sustain pedal troubleshooting table
Separate polarity from connection and hardware faults.
This order avoids buying adapters or replacing a pedal before the simplest controlled tests are complete.
| Symptom | Likely area | First check |
|---|---|---|
| Sustain works backward | Polarity | Power off and switch |
| No response | Jack or compatibility | Confirm exact port |
| Intermittent response | Cable or plug | Direct connection |
| Only app is wrong | MIDI/software | Test piano sound |
Review piano accessories, digital pianos and the warranty page for current product context.
Stop when the model documentation does not confirm compatibility. An official answer is safer than experimenting with undocumented wiring or opening a pedal. Label the working pedal and switch position if several keyboards or pedals share the same practice space, and keep the cable loosely coiled. Retest it after moving the piano.
Frequently asked questions
How do you switch polarity on a sustain pedal?
Turn the piano off, remove your foot from the pedal, move the pedal’s polarity switch to the other marked position, reconnect it fully and power on without pressing it. Then test one chord. Follow the model manual if it specifies a different startup sequence.
Why does my sustain pedal work backwards?
The pedal and piano may expect opposite resting electrical states, or the piano may have detected the pedal while it was pressed during startup. Reconnect with power off, keep the pedal released while starting and use the polarity switch only when the pedal supports one.
How do you know whether a sustain pedal is working?
Play and release a note without the pedal; it should decay normally. Repeat while holding the pedal; the note should continue, then clear when the pedal rises. Test several slow cycles and confirm the behavior through the piano before adding an app or MIDI connection.
Next step: Use the checklist above with the exact model, device and learning goal, then verify current specifications on the relevant product page before buying or changing the setup.
