This is a full piano-roll editor, not a viewer. Notes can be moved, lengthened, shortened, deleted and drawn in; velocity is editable per note; multiple tracks are supported, each with its own instrument assignment. Playback runs through a bundled SoundFont so you hear the edit rather than having to imagine it.
Online MIDI Editor With a Piano Roll
Open a MIDI file, edit notes on a piano roll and save it back out. The editor runs in your browser with a built-in SoundFont, so nothing is uploaded.
Open a MIDI file, move notes around on a piano roll, hear it play through a built-in instrument, and save the result back out. The whole editor runs inside this page.
MIDI files only · edits happen in your browser · nothing is uploaded
Loading the editor…
01
What the Editor Does
It is the same editor as the open-source signal project, loaded in a frame on this page. That means it behaves like a desktop MIDI editor rather than a simplified web widget, including keyboard shortcuts and a proper transport.
Everything happens on your own machine. Opening a file reads it from your disk into the editor; saving writes a MIDI file back to your downloads. Nothing is uploaded, nothing is stored on a server, and the tool costs no credits.
02
Opening and Saving
Use the open button above the editor rather than the editor's own file menu — that is what hands the file across into the frame, and it is also what tells this page what to name the result when you save.
Saving asks the editor for the current state and writes it out as a standard MIDI file. The download keeps the name of the file you opened, with a .mid extension, so a round trip does not quietly rename your work.
The editor takes a moment to load the first time because the bundle and its instrument samples are a few megabytes. After that it is cached by the browser. If it ever fails to appear, the reload button under the frame remounts it without reloading the whole page.
03
Where the MIDI Comes From
Three tools on this site produce MIDI that lands naturally in this editor. Audio to MIDI transcribes an existing recording, which usually needs exactly the kind of cleanup a piano roll is good at: deleting stray short notes around loud onsets, and extending notes the transcription cut early.
The AI MIDI generator writes a short phrase from a key and a part. Generated phrases almost always want one or two notes nudged and the last note trimmed so the loop joins cleanly, which is a minute of work here.
If you are starting from audio and do not know its tempo, run the key and tempo finder first and set that tempo in the editor, so the bar lines land where the music actually is. A piano roll with the wrong grid is harder to read than no grid at all.
04
What It Is Not For
This edits notes, not sound. The bundled instrument is there so you can hear what you are doing; it is not a sound library to produce finished music with. When the notes are right, take the MIDI into a DAW and play it through whatever instrument the track actually needs.
It is also not an audio editor. If what you have is a recording rather than a MIDI file, nothing here applies — the audio cutter trims recordings and the stem splitter separates them.
Large files are the practical limit. A few thousand notes across several tracks is comfortable; an orchestral score exported as one dense MIDI file will feel heavy in a browser in a way it would not in desktop software.
05
Nothing Is Uploaded
The editor is served as static files from this site and runs entirely in your browser. The file you open is read locally and the file you save is written locally. No request carries your music anywhere.
That is worth knowing if you are editing unreleased material or work for a client. Web-based editors that process server-side necessarily receive a copy of whatever you open; this one does not have the option, because there is no server step in the path.
Once the page and the editor bundle have loaded, it also works with no connection at all.
06
MIDI Editor Questions
Is my file uploaded?
No. The editor runs in your browser as static files. The file you open is read from your device and the file you save is written back to it, with no server step in between.
Can I hear what I am editing?
Yes. A SoundFont ships with the editor, so playback uses a real instrument rather than a synthesised beep. It is for monitoring your edit, not for producing a final sound.
Why does it take a few seconds to appear?
The editor bundle and its instrument samples are a few megabytes. The first load fetches them; after that the browser caches them and it opens quickly.
Should I open files with the button or the editor's own menu?
Use the button above the frame. It hands the file across correctly and tells this page what to name the result when you save.
Can I edit audio here?
No. This edits MIDI, which is notes and timing. For a recording, use the audio cutter to trim it or the stem splitter to separate it.
Does it cost credits?
No. Everything runs on your device, so there is nothing to meter.
What happens to my work if I reload?
It is lost — the editor holds state in memory only. Save the MIDI before leaving or reloading the page.
Can I change the instrument a track plays through?
Yes, each track can be assigned a different program from the bundled SoundFont. That only affects what you hear here — a MIDI file stores the program number, and the DAW you import it into may well override it with whatever instrument is loaded on that track.
Does it handle multiple tracks?
It does. Tracks appear separately and can be edited and muted independently, which is the normal way to work on a chord part and a melody without them visually colliding on one roll.
Why is the editor in English when the rest of the page is not?
The editor is a prebuilt open-source application loaded in a frame, and its interface language is fixed in that build. Everything outside the frame follows your chosen language.