MIDI Player

Drag in or upload a MIDI file to see its notes on a piano roll and play it back in your browser. Adjust tempo and instrument on the fly. Everything runs locally; your file never leaves your device.

How It Works

A MIDI file does not contain audio; it stores a list of notes — which key, how loud, when it starts, and when it ends — much like sheet music. This tool reads that data entirely in your browser using html-midi-player (built on Magenta.js and Tone.js) and turns it into two things:

• Piano roll: each note is drawn as a horizontal bar. Pitch runs bottom-to-top, time runs left-to-right, so you can see the melody and chords at a glance. Notes light up as they play.
• Playback: the notes are synthesized live using a soundfont, so no server is involved. Hit play on the transport bar to listen.

Controls

• Instrument: switch the soundfont. General MIDI honours the instrument written in the file, Grand Piano forces a piano sample, and Synth uses a lightweight built-in oscillator (loads instantly, no download).
• Tempo: slow the piece down to 0.25× to study a passage, or speed it up to 2×. The piano roll re-scales to match.

Privacy

Your MIDI file is read with the browser's FileReader and processed on your machine. It is never uploaded. Soundfont samples are streamed from a public CDN only when you choose an instrument that needs them.