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MIDI Editor

MIDI Editor in ComfyTV

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What this node does

MIDI Editor is an in-browser piano roll that works in the time domain (seconds) rather than beats — the horizontal grid is real time, so it’s built for editing actual MIDI performances. You draw notes on the grid, organize them into MIDI channels (each with a General MIDI instrument, plus a dedicated drum channel), mute/solo channels while you work, and shape velocity. Press ▶ Run to write a Standard MIDI File on the backend; the midi output is a COMFYTV_AUDIO payload pointing at the exported .mid. Running with an empty roll fails with “the piano roll is empty”. You can import a wired MIDI file (midi input, COMFYTV_AUDIO) into the roll — its channels, programs and tempo map come in, ready to edit.

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The editor

The card is a toolbar-plus-piano-roll, laid out in the time domain. Tool row.
  • Draw / Select — the two editing modes.
    • Draw: click-drag on the grid to create a note; the drag sets its duration and it beeps as you place it.
    • Select: drag a marquee to select (Shift adds); click a note to grab it.
  • Play (▶ / ■) — plays the roll with a built-in oscillator/drum synth using look-ahead scheduling; a green playhead sweeps in real time and muted channels stay silent.
  • Snap — time snapping: free, 10ms, 50ms, 100ms, 250ms, or 1s.
  • Undo (↩), Clear channel, and (when a MIDI file is wired) Import MIDI. Import errors show here.
Channel row. Each MIDI channel is a chip showing a color swatch and its number (Ch1…), or 🥁 for the drum channel (channel 10 / index 9). Per chip:
  • click the chip to make that channel active,
  • S solos the channel (mutes all others),
  • the volume icon mutes/unmutes it,
  • hovering a chip highlights just that channel in the roll (others dim). ＋ adds a channel, ＋🥁 adds the drum channel (only if there isn’t one), − removes the active channel. For non-drum channels, an Instrument dropdown sets the General MIDI program.
Piano roll. A scrollable grid with a piano keyboard down the left (click a key to audition; C notes labelled; drum channels show GM drum names). A time ruler across the top marks seconds (tick spacing adapts to zoom). Notes are color-coded by channel/instrument and can be:
  • moved by dragging the body,
  • resized from the left or right edge handle,
  • deleted by double-clicking,
  • multi-selected and edited together. Notes on inactive channels appear as dim “ghost” blocks in their channel color. A velocity lane along the bottom paints 0–127 velocity for the notes under the cursor.
Zoom & navigation. Ctrl/Cmd + mouse wheel zooms the time axis; scroll bars pan. Shortcuts: Delete/Backspace removes selected notes, Ctrl/Cmd+Z undoes, Ctrl/Cmd+A selects all.

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Workflow / step by step

  1. (Optional) wire a MIDI file and press Import MIDI to load its channels, programs and tempo map.
  2. Pick a Snap value; select a channel and set its Instrument (or add 🥁 for drums).
  3. Draw or edit notes; drag the edge handles to trim durations.
  4. Use S/mute on channels to isolate parts while you work; shape dynamics in the velocity lane.
  5. Press Play to audition; use ghost notes to align across channels.
  6. Press ▶ Run to export the midi file, then feed it to Score Synth (to render audio) or download it.

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Inputs and outputs

The roll (events, channel programs and tempo map) is stored on the node in a hidden events_json field, so it’s saved with the workflow. Mute/solo state is a live playback aid and is not part of the export.

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Tips

  • This is the seconds-domain editor — positions are real time, not beats. For beat/bar composing that becomes MusicXML, use Score Editor instead.
  • Solo (S) is the fast way to hear one channel; it mutes everything else until you toggle it off. Mute/solo only affects the in-editor preview, not the exported file.
  • Importing a MIDI file brings in its tempo map and per-channel programs — a good starting point for cleanup.
  • The exported .mid is COMFYTV_AUDIO; feed it to Score Synth to hear it with a SoundFont.
  • Score Editor — the beats-domain piano roll that outputs MusicXML.
  • Score Performer — outputs a MIDI file from a written score.
  • Score Synth — renders the exported MIDI to audio via a SoundFont.
  • Bridge — convert COMFYTV_AUDIO to/from native ComfyUI. See https://github.com/jtydhr88/ComfyTV/blob/main/docs/bridges.md