Groove Builder

Generate idiomatic drum patterns by genre with proper humanization. Writes to MIDI clips on the user's drum track.

Workflow

1. Identify genre + tempo

Required: genre. Optional: tempo (use genre defaults).

2. Verify drum rack

get_track_info on the drum track. Confirm a drum rack is loaded with at least kick (C1), snare (D1), hat (F#1), and optionally clap (D#1), open hat (A#1), perc (G1+).

If no kit loaded → ask user, or load stock Ableton Drum Kit.

3. Write the pattern

For a 1-bar (16-step) pattern, here are tested templates:

#### Lo-fi hip-hop

Kick:  X . . . . . X . . . . . . . . .
Snare: . . . . X . . . . . . . X . . .   (snare on 5 & 13 for half-time feel)
Hat:   X . X . X . X . X . X . X . X .   (8th notes)

• Kick: vel 100-110
• Snare: vel 90-100, slight late timing (+5ms)
• Hat: vel 65-85, ±15 humanize, swing 8-12%

#### Boom-bap

Kick:  X . . X . . X . . . X . . . . .
Snare: . . . . X . . . . . . . X . . .
Hat:   X X X X X X X X X X X X X X X X   (16ths)

• Hat: vel 50-80, more aggressive humanize ±20

#### Trap

Kick:  X . . . . . . X . . . . . . . .   (sparse, half-time feel)
Snare: . . . . X . . . . . . . X . . .
Hat:   X X . X X X . X X . X X X . X X   (rolling, with stutters)
808:   long held bass notes underneath

• Hi-hat rolls: alternate 16ths with 32nd-note bursts
• Open hat occasionally on the off-beat

#### House

Kick:  X . . . X . . . X . . . X . . .   (4-on-the-floor)
Clap:  . . . . X . . . . . . . X . . .
Hat:   . . X . . . X . . . X . . . X .   (off-beat 8ths)
OpHat: . X . . . X . . . X . . . X . .   (between beats)

• Kick: vel 110, locked on grid
• Clap: vel 95
• Hat: tight, minimal humanize

#### DnB

Kick:  X . . . . . . . . . X . . . . .
Snare: . . . . X . . . . . . . X . . .
Hat:   X X X X X X X X X X X X X X X X   (16ths, fast)

• Snare on 2 & 4 (half-time feel at the bar level)
• Add ghost notes on snare at velocity 30-50

4. Humanize

After writing, apply genre-appropriate humanization:

• Lo-fi: heavy (±20 velocity, ±15ms timing, 12% swing)
• Boom-bap: medium (±15 velocity, ±10ms, 6-8% swing)
• House/Techno: minimal (±5 velocity, ±2ms, 0% swing)
• Trap: moderate on hats, tight on kick/snare
• DnB: tight on kick/snare, loose on hats

5. Add fill (optional)

If user wants a 2-bar pattern with fill:

• Bar 1: main pattern
• Bar 2: same, but last 1-2 beats replaced with a fill (snare roll, tom run, hat stutter)

6. Confirm + write

Summarize: "Lo-fi pattern, 90 BPM. Kick on 1+3, snare on 5+13, 8th hats with 12% swing. ±15 velocity, ±15ms timing. Apply?"

Don'ts

• Don't write 100% on-grid for any genre except minimal techno or hard EDM.
• Don't overdo ghost notes (>4 per bar starts to clutter).
• Don't apply genre defaults if the user gave a specific tempo — respect their tempo.
• Don't write more than 8 bars in one shot — give the user a section to evaluate.