What Is a Sustain Pedal?
Updated Nov 11, 2026 · By 
Jonah Mercer · Editorial policy
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A sustain pedal is a foot pedal that holds notes sounding after you lift your fingers. It plugs into the sustain input on a digital piano, MIDI keyboard or synthesizer with a 1/4-inch plug, and a polarity switch matches it to the keyboard. Press it to hold a note, and lift your foot to stop the sound.
What the pedal does
A sustain pedal holds the notes you play so they keep sounding after your fingers leave the keys. On a digital piano or MIDI keyboard, pressing the pedal sends a sustain signal to the instrument, and the notes ring on until you lift your foot. That is the whole job of the pedal: it adds hold to notes and chords without changing which notes you play. The pedal itself makes no sound; the keyboard or piano makes the sound, and the pedal only controls how long it lasts.
Plug it into the sustain input
Each pedal here connects with a 1/4-inch plug: the M-AUDIO SP-2 has a 6 foot cable, the SP-1 has a 5ft cable, the karmiero has a 91 inch cable with a 1/4 inch (6.35mm) jack, and the UPELLA has a 6.25 feet cable with a 1/4 inch straight plug. Plug the cable into the sustain pedal input on your keyboard or digital piano, not into an audio input. The pedal works as a switch for the keyboard.
Set the polarity switch
All four pedals here have a polarity switch. Keyboards expect the pedal to work one of two ways, normally open or normally closed, and the switch matches the pedal to the keyboard. If notes keep sounding when you are not pressing the pedal, flip the switch on the side of the pedal, then press a key to check. Plug the pedal in, turn on the keyboard, press a key, and flip the switch if the note holds without the pedal down.
Pick the size and shape
The M-AUDIO SP-2 is a piano-style pedal at 10.5 by 3 by 2.5 inches with a chrome foot pedal and rubber pads underneath that grip the floor. The SP-1 is a compact pedal at 6.5 by 6 by 3 inches with a slip-resistant ridged footrest. The karmiero pedal is 8.6 by 6.5 by 6 inches with a rubber bottom and a spring design, and the UPELLA has 4 non-slip rubbers at the bottom and a memory spring. Choose the shape that fits under your keyboard and stays put on your floor.
What you need
M-AUDIO SP-2 Universal Sustain Pedal Classic Piano-Style
A piano-style sustain pedal with a chrome foot pedal, a polarity switch, rubber pads underneath and a 6 foot cable with a 1/4 inch jack.
- Polarity switch
- Piano-style pedal
M-AUDIO SP-1 Universal Sustain Pedal Compact Sustain
A compact sustain pedal with a polarity switch, a slip-resistant ridged footrest and a 5ft cable with a 1/4 inch phone plug.
- Polarity switch
karmiero Sustain Pedal for Keyboard Universal
A sustain pedal in alloy and plastic with a polarity switch, a rubber bottom, a spring design and a 91 inch cable with a 1/4 inch jack.
- Polarity switch
UPELLA Universal Sustain Pedal for Digital Piano
A sustain pedal in ABS plastic and alloy steel with a polarity switch, 4 non-slip rubbers underneath and a 6.25 feet cable with a 1/4 inch plug.
- Polarity switch
These come from our ranked list Best Sustain Pedal, which compares them spec by spec.
Frequently asked questions
Do all sustain pedals need a polarity switch?
No. The four pedals here each have a polarity switch, and it matches the pedal to the keyboard. If notes hold without the pedal down, flip the switch and press a key to check.
Can I use a sustain pedal with any keyboard?
The M-AUDIO pedals list compatibility with MIDI keyboards, pianos and synthesizers, and the karmiero and UPELLA pedals list MIDI keyboards and digital pianos. Check that your keyboard has a sustain pedal input before you buy.
How long are the cables on these pedals?
The M-AUDIO SP-2 has a 6 foot cable, the SP-1 has a 5ft cable, the karmiero has a 91 inch cable, and the UPELLA has a 6.25 feet cable. Pick the length that lets the pedal sit where your foot rests.
Ranked sustain pedals lists
More how-to guides
Product details come from each Amazon listing and can change. Check the listing before you buy.