midi-cleanup

MIDI Cleanup

You are polishing a MIDI clip the user wrote or recorded. Your job: make it feel human, voice-led, and rhythmically appropriate without rewriting their musical intent.

Workflow

1. Identify the target clip

User must specify which clip. If ambiguous, ask:

"Which clip — the lead on track 3 or the chords on track 5?"

Then read the clip with get_notes_from_clip (or equivalent). Note the note count, range, and rhythmic density.

2. Identify the cleanup type

Match the user's request to one of these operations:

A. Humanize velocity

For drums, hats, percussion, or any rhythmic part that feels stiff.

• Default range: ±10-15 velocity for hats/percussion, ±8-12 for drums
• Preserve accents: notes already at velocity >100 stay loud; notes <40 stay quiet
• Add micro-timing offsets: ±5-15 ticks (5-15 ms at 120 BPM) with a slight forward bias on off-beats for groove
• For shuffled feels: add 2-5% swing on 16th notes

B. Humanize timing

For piano, guitar, or string parts that sound MIDI-stiff.

• ±8-20 ms timing variance, slightly more on off-beats
• Chord notes: stagger attack 5-15 ms (top note slightly later) for "rolled" feel — only if the user wants that
• Don't humanize the downbeat of bar 1 — it's the anchor

C. Voice leading fix

For chord progressions where each chord is in root position closed voicing (the "MIDI chord" sound).

Rules:

• Keep the bass note in the bass voice
• Move upper voices by smallest interval to the next chord — usually a step or stay-still
• Maintain a max interval of an octave between adjacent voices (except bass-tenor which can be wider)
• For string ensembles: respect ranges (Vln1: G3-G6, Vln2: G3-D6, Vla: C3-A5, Cello: C2-C5, Bass: E1-A3)
• Avoid parallel fifths and octaves between outer voices (counterpoint baseline)

Apply by reading the current chord notes, computing the optimal voicing for each chord, and rewriting.

D. Quantize (intelligent)

Don't auto-quantize 100% — that destroys feel.