Online Piano

How it is calculated

This online piano has five octaves (C2 to C7) and can be played with a mouse, your fingers or your computer keyboard – polyphonic, too. The sound is computed in your browser as you play; no piano recordings are loaded.

How to play

• Mouse or touch: click or tap the keys. Use several fingers for chords; sliding across the keys makes a glissando.
• Computer keyboard: the middle letter row plays the white keys (A = C, S = D, D = E, F = F, G = G, H = A, J = B, K = C …), the row above plays the black keys (W = C♯, E = D♯, T = F♯, Y = G♯, U = A♯). The mapping is shown on the keys.
• Change octave: with the arrow keys ← → or the octave menu.
• Sustain: hold the space bar or switch on the sustain button – released notes keep ringing, like with the right pedal.
• On a phone the keyboard is wider than the screen: page with ◀ ▶, swipe sideways in the grey strip below the keys or pick an octave.

Note names and octave numbers

Keys are labelled in scientific pitch notation: the letter names the note and the number the octave. C4 is middle C in the centre of the keyboard. Black keys are labelled with sharps (C♯, D♯, F♯, G♯, A♯); depending on the key signature the same keys are also called D♭, E♭, G♭, A♭ and B♭. Good to know: in German the note B is called H, and a German B means B♭.

How the notes are calculated

The piano uses equal temperament: every semitone is higher than the previous one by a factor of 2^1/12 ≈ 1.0595, and twelve semitones exactly double the frequency (an octave). The reference is concert pitch A4 = 440 Hz (ISO 16). So f = 440 Hz · 2^{(n − 69)/12} with the MIDI number n – for example, middle C4 = 261.63 Hz. The sound is built additively: overtones (whole-number multiples) of decreasing loudness are added to the fundamental, shaped by an envelope with a fast attack and slow decay, longer for low notes than for high ones.

Honest limits

• The sound is synthesised: it sounds like a piano, but not like a sampled concert grand. A computer keyboard cannot sense how hard you press, so all notes are equally loud.
• Many computer keyboards only detect a limited number of keys pressed at once (often 3 to 6). With large chords some notes drop out – that’s the hardware.
• Depending on device and browser there is a small delay between key press and sound; wired headphones usually have less than Bluetooth.
• It doesn’t replace a real instrument or lessons – but it’s great for trying things out, picking out melodies and learning note names.

Privacy

All notes are computed in your browser with the Web Audio API. Nothing is recorded, uploaded or stored.

A key doesn’t sound? Use the keyboard test to check whether your computer keyboard registers every key press.

Frequently asked questions

Sources and legal basis

• ISO 16:1975 – Acoustics: Standard tuning frequency (standard musical pitch)
• MDN Web Docs – PeriodicWave (Web Audio API)
• Wikipedia – Piano key frequencies

As of: 28 September 2026