Guide
Playing and inspecting a MIDI file: piano roll, tempo, tracks and a simple synthesizer
A MIDI file is a recipe, not a recording. It lists which notes to play, when, for how long and how hard, on which channel, along with tempo changes and a few other messages. Because it holds no audio, files are tiny, and a whole symphony fits in a few dozen kilobytes. This page opens one, plays it and shows what is inside as a piano roll, so you can learn a part, check an export or just see how a piece is built.
What the page shows
After you drop a file, the summary lists its name, length in minutes and seconds, tempo in BPM, the time signature, the number of notes and the format. If the tempo changes during the piece, the page adds “(changes)”. Below it is a piano roll: time runs left to right and pitch runs from low to high, with each note a bar coloured by track. Below the roll, the lowest and highest notes of the file are named, which is useful for checking whether a part fits an instrument.
A worked example
Press Sample to open a built-in file called C major scale. The summary says it is format 0, with 22 notes, a tempo of 120 BPM, a time signature of 4/4 and a length of 5 seconds. The lowest note is C3 and the highest C5. Press Play and the scale runs up and back down; the playhead moves across the roll and the time counter advances. Click the roll to jump to a note, and the sound restarts from there.
Tracks and channels
A format-1 file keeps each instrument on its own track. The page shows a chip for each, named from the file, and you can switch a chip off to silence that track, then listen to the bass line alone or leave out the melody to practise it. Drums use channel 10 in General MIDI and play here as short noise bursts rather than a drum kit. Colours help to tell the tracks apart on the roll.
Speed and zoom
The speed slider goes from 25 to 200 percent, which is a quick way to slow a fast passage, but changing it restarts playback. Because the file only stores notes, slowing the playback does not change the pitch. The follow option zooms the roll to a 20-second window around the playhead, so long files stay readable. Volume is separate from the system volume.
The sound
The synthesizer gives one soft tone per note. It makes no attempt to imitate a piano, a guitar or a violin, and the instrument chosen in the file does not change the sound. That is enough to hear the notes and the rhythm; for a realistic rendering, use a DAW or a player with a soundfont.
Edge cases
Files with several tempo changes show a tempo with a note that it changes. Corrupt or non-MIDI files show an error message instead of playing. The file picker accepts .mid and .midi, so rename other extensions of standard MIDI files if needed.
Limits
It does not edit, convert or save files. It does not support soundfonts or external MIDI devices. Everything is read and played locally, and nothing is stored.
Related tools
- Virtual Piano plays the same kind of synthesizer sound from a keyboard.
- Note Frequency Chart lists the pitch of each note you see on the roll.
- Tap Tempo measures a tempo to compare with the file’s.
- Audio Converter converts a recording of the playback to another format.
Checked against the current version of the MIDI File Player & Piano Roll on .