IconVault's Piano Keyboard is a playable virtual piano that needs no install or download. Play with mouse or touch on the on-screen keys, or use your computer keyboard as the instrument: the Z row plays the lower octave and the Q row plays the upper octave, chromatically from C to B. Sound is synthesized live with the Web Audio API, so every key press rings out instantly.

You get an octave shift control (octaves 1 to 6), a sustain toggle that lengthens note release, and a note sequence recorder that logs every note you play as names like C4 and E4, which you can copy to your clipboard. It is free and runs fully in your browser. The honest note: notes use a simple triangle-wave synth voice, so it sounds like a clean electronic tone rather than a sampled grand piano.