MIDI File Visualizer

How to view and play a MIDI file

1. Drop a .mid or .midi file on the drop zone, or click it to choose one. No file at hand? Press Load demo song to open a short “Frère Jacques” round with bass and drums.
2. The piano roll appears at once. Each coloured bar is a note: its vertical position is the pitch (C labels mark every octave), its length is the duration, and brighter bars were played harder (higher velocity).
3. Press Play to hear the file through a simple built-in synthesizer. The red cursor follows the music and the notes that are sounding light up. Pause keeps the position; Stop goes back to the start.
4. Click anywhere on the piano roll to move the cursor to that moment, even during playback.
5. Choose a View: Whole song fits the entire file on screen, while the 5, 10 and 20-second windows zoom in and scroll with the cursor, which is easier to read for dense piano parts.
6. In Tracks, untick a track to mute it. It turns grey on the piano roll so you can focus on one part, for example to learn a melody or a bass line.

The file is read by JavaScript in this tab. Nothing is uploaded.

What the numbers mean

• Duration: the length of the song in minutes and seconds, computed from the tempo map, so tempo changes are taken into account.
• Tempo (BPM): the tempo at the start of the song in beats (quarter notes) per minute. When the tempo changes during the song, the lowest and highest values are shown in brackets. A file without a tempo event plays at the MIDI default of 120 BPM.
• Notes: the number of notes, after pairing every note-on with its note-off.
• Tracks with notes / total: format 1 files usually start with a “conductor” track that only holds tempo and time signature, so the two counts often differ by one.
• Time signature, Note range (lowest and highest note, with middle C written C4) and SMF format (0 = one track holding all channels, 1 = several synchronised tracks).

How the parser works

A Standard MIDI File is a header chunk (MThd) followed by track chunks (MTrk). Each event is preceded by a delta time in ticks, and the header gives the number of ticks per quarter note. This tool reads the file byte by byte: it follows running status (where a status byte is omitted and the previous one is reused), skips SysEx messages and unknown chunks, reads tempo, time signature and track name meta events, and treats a note-on with velocity 0 as a note-off, as most sequencers write them. Ticks are then converted to seconds with the tempo map. Files that use an SMPTE time base (frames per second) are also supported.

Limits of the built-in synth

Playback is meant to check the notes, not to sound like a real instrument. Every melodic channel uses the same soft triangle wave, whatever the program (instrument) number. On channel 10, the General MIDI percussion channel, kicks are a falling sine and the other drums are short noise bursts. Pitch bend, sustain pedal and controllers are ignored. For realistic sound, open the file in a DAW or a player with a SoundFont.