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MIDI Editing

ScratchTrack includes a piano roll editor for composing MIDI parts. You can draw notes, adjust velocity, and use Audio Unit instruments to play them back.

Adding a MIDI Track

  1. Click Add Track in the song editor.
  2. Select MIDI Track.
  3. A new MIDI track appears in the timeline.

MIDI tracks use a built-in General MIDI sampler by default. You can assign an Audio Unit instrument for more sounds (see Mixing & Effects).

Creating a MIDI Clip

To add notes, you first need a MIDI clip on your track:

  1. Create a MIDI clip on the MIDI track.
  2. Set the clip's start position (in beats) and duration (in bars/beats).
  3. Double-click the clip to open the Piano Roll Editor.

The Piano Roll Editor

Piano roll editor

The piano roll displays a grid where:

  • The vertical axis represents pitch (C-1 to G9, all 128 MIDI notes)
  • The horizontal axis represents time (in beats)
  • The piano keyboard on the left lets you audition notes by clicking keys

Tools

The piano roll has three tools, accessible from the toolbar:

Tool Action
Select Click notes to select them. ++shift++ -click to multi-select. Drag to move notes.
Draw Click and drag to create new notes. The note length follows the grid.
Erase Click a note to delete it.

Drawing Notes

  1. Select the Draw tool.
  2. Click on the grid where you want the note to start.
  3. Drag right to set the note's duration.
  4. Release to place the note.

Editing Notes

  • Move a note — Select it and drag to a new position (changes pitch and timing)
  • Resize a note — Drag the right edge to change its duration
  • Delete a note — Use the Erase tool and click, or right-click and select Delete
  • Edit details — Double-click a note to open a detail popover

Snap to Grid

Toggle Snap to Grid to align notes to the beat grid (sixteenth-note precision). When enabled:

  • New notes snap to the nearest grid line
  • Moving notes snaps to grid positions
  • Resizing snaps note endpoints

Disable snap for free-form timing adjustments.

Zoom

Use the zoom controls to adjust the horizontal view:

  • Zoom in (up to 400%) for detailed editing
  • Zoom out (down to 25%) for an overview

Velocity

Velocity controls how hard a note is played (1–127). Higher velocity = louder and more intense.

Adjusting Velocity

  1. Select a note.
  2. Use the velocity slider (1–127) to set the value.

Visual Feedback

Notes are color-coded by velocity:

  • Cool blue — Soft/quiet notes (low velocity)
  • Warm colors — Loud/intense notes (high velocity)

MIDI Input

ScratchTrack supports external MIDI controllers:

  1. Connect a MIDI controller to your Mac.
  2. MIDI input is automatically detected via CoreMIDI.
  3. Play notes on your controller — they're captured in real-time.

Supported MIDI messages

  • Note On / Note Off
  • Control Change (CC)

Playback

MIDI tracks play back through the assigned instrument:

  • Default — General MIDI sampler
  • Audio Unit — Any installed AUv3 instrument plugin

MIDI timing is beat-based, calculated from your song's tempo setting.

Next Steps