Rigidity Check

The four checks

1. Velocity uniformity

Detection: For each track, count notes by velocity value. If more than 60% of a track's notes share a single velocity, flag moderate. If 100% share, flag critical. Ignore ghost-notes (velocity <40 or articulation: 'ghost') — they're deliberately uniform.

Fix: Apply velocityCurve from tools/compose-helpers/humanize.ts with style 'natural' — emphasizes downbeats by +8 and softens offbeats by −4. For tracks that should already have a deliberate shape (leads, fills), use 'accented-downbeats' instead.

2. Bar-to-bar identicalness

Detection: For each track, walk consecutive bars and compare the set of notes within each. Two bars are "identical" if they contain the same pitches at the same within-bar time offsets with the same velocities. Flag runs of 4+ consecutive identical bars as moderate.

Fix: For each run of length N, introduce one variation at the middle bar. Options (pick one per run):

• Drop one hit (e.g., remove a kick on beat 3)
• Add a ghost note between existing hits
• Bump one note's velocity by ±15
• Swap one pitch for a neighboring chord tone
• Add a short fill in the last beat of the middle bar

3. Section contrast

Detection: For each adjacent section pair, compare:

• Instrument set — the instrumentId values present in each section's tracks
• Note density — total notes divided by bar count, within 10% of each other
• Dominant register — the MIDI range covering >80% of notes, within ±1 octave

If all three match between adjacent sections, flag as moderate. Two different sections shouldn't be indistinguishable at the structural level.

Fix: This is a judgment call based on section role. Options (pick what fits the energy arc):

• Drop one instrument in the later section (thinning)
• Add an instrument in the later section (building)
• Swap drum pattern (e.g., from fourOnFloor to halfTime, or vice versa)
• Shift register up or down by an octave
• Raise or lower overall dynamics by ~15 velocity points

4. Transition markers

Detection: For each section boundary, examine the last bar of section N and the first bar of section N+1. A transition is "marked" if any of the following is present within 1 bar of the boundary:

• A crash, ride, or cymbal hit
• A fill (rapid succession of 4+ notes on a drum or melodic instrument)
• A rest (empty bar or drop-out of most tracks)
• A velocity swell of >15 points across 2+ notes
• An FX hit (impact, riser, sweep from a oneshot track)
• An automation point

If none of these are present, flag as moderate (flat transition).

Fix: Add one marker at the boundary. Options:

• Add a crash on beat 1 of section N+1
• Drop out the kick in the last beat of section N (kick drop-out)
• Add a snare fill in the last half-bar of section N (four snare hits at 16th intervals)
• Add an FX impact at the downbeat of section N+1
• Add a volume ramp automation on one track over the last 2 beats of section N

Do Not

• Apply fixes without explicit user confirmation
• Overwrite the source file without going through the draft-first convention
• Add fills, instruments, or variations beyond what the specific finding calls for
• Rewrite sections the user didn't ask about
• Audit schema-invalid compositions — stop and report the validation error instead
• Flag deliberate uniformity as a problem: ghost notes, sub-bass drones, and long held pads are supposed to be uniform