"""
Scythe MCP - Drum Pattern Generator
Genre-specific drum patterns for electronic, hip-hop, rock, and more.
"""
from typing import List, Dict, Optional
from dataclasses import dataclass
import random
from ..music_theory.rhythm import Note, Rhythm
# Standard GM drum map (MIDI notes)
DRUM_MAP = {
"kick": 36,
"snare": 38,
"clap": 39,
"closed_hat": 42,
"open_hat": 46,
"low_tom": 45,
"mid_tom": 47,
"high_tom": 50,
"crash": 49,
"ride": 51,
"rimshot": 37,
"cowbell": 56,
"tambourine": 54,
"shaker": 70,
}
# 808-style drum map (common in hip-hop/trap)
DRUM_MAP_808 = {
"kick": 36,
"snare": 38,
"clap": 39,
"closed_hat": 42,
"open_hat": 46,
"perc1": 75,
"perc2": 67,
}
@dataclass
class DrumPattern:
"""A complete drum pattern with multiple instruments."""
name: str
bars: int
bpm: float
time_signature: tuple
tracks: Dict[str, Rhythm] # instrument -> rhythm
def to_midi_notes(self, drum_map: Dict[str, int] = None) -> List[Dict]:
"""Convert all tracks to MIDI note list."""
if drum_map is None:
drum_map = DRUM_MAP
all_notes = []
for instrument, rhythm in self.tracks.items():
pitch = drum_map.get(instrument, 36)
for note in rhythm.notes:
all_notes.append({
"pitch": pitch,
"start": note.start,
"duration": note.duration,
"velocity": note.velocity
})
# Sort by start time
all_notes.sort(key=lambda n: n["start"])
return all_notes
# =============================================================================
# GENRE PATTERNS
# =============================================================================
def _create_four_on_floor(bars: int = 4, velocity: int = 100) -> Rhythm:
"""Classic house/techno kick pattern."""
notes = []
for bar in range(bars):
for beat in range(4):
notes.append(Note(
start=bar * 4 + beat,
duration=0.25,
velocity=velocity,
pitch=DRUM_MAP["kick"]
))
return Rhythm((4, 4), notes, bars * 4)
def _create_boom_bap_kick(bars: int = 4, velocity: int = 100) -> Rhythm:
"""Hip-hop boom bap kick pattern."""
patterns = [
[0.0, 1.75, 3.0], # Classic
[0.0, 0.75, 2.75], # Variation 1
[0.0, 1.5, 2.5, 3.5], # Variation 2
]
pattern = random.choice(patterns)
notes = []
for bar in range(bars):
for pos in pattern:
notes.append(Note(
start=bar * 4 + pos,
duration=0.25,
velocity=velocity + random.randint(-5, 5),
pitch=DRUM_MAP["kick"]
))
return Rhythm((4, 4), notes, bars * 4)
def _create_trap_hihat(bars: int = 4, velocity: int = 80) -> Rhythm:
"""Trap-style hihat with rolls."""
notes = []
for bar in range(bars):
for beat in range(4):
# Regular eighth notes
for eighth in range(2):
pos = bar * 4 + beat + (eighth * 0.5)
notes.append(Note(
start=pos,
duration=0.125,
velocity=velocity - (eighth * 10),
pitch=DRUM_MAP["closed_hat"]
))
# Occasional triplet rolls
if random.random() < 0.25:
for triplet in range(3):
pos = bar * 4 + beat + (triplet / 6) + 0.5
notes.append(Note(
start=pos,
duration=0.08,
velocity=velocity - 20,
pitch=DRUM_MAP["closed_hat"]
))
return Rhythm((4, 4), notes, bars * 4)
def _create_backbeat_snare(bars: int = 4, velocity: int = 100) -> Rhythm:
"""Standard backbeat snare on 2 and 4."""
notes = []
for bar in range(bars):
for beat in [1, 3]: # 2 and 4 (0-indexed)
notes.append(Note(
start=bar * 4 + beat,
duration=0.25,
velocity=velocity,
pitch=DRUM_MAP["snare"]
))
return Rhythm((4, 4), notes, bars * 4)
def _create_offbeat_hat(bars: int = 4, velocity: int = 70) -> Rhythm:
"""Offbeat hi-hat pattern (disco/house)."""
notes = []
for bar in range(bars):
for beat in range(4):
notes.append(Note(
start=bar * 4 + beat + 0.5,
duration=0.25,
velocity=velocity,
pitch=DRUM_MAP["open_hat"]
))
return Rhythm((4, 4), notes, bars * 4)
def _create_eighth_hat(bars: int = 4, velocity: int = 65) -> Rhythm:
"""Straight eighth note hi-hats."""
notes = []
for bar in range(bars):
for beat in range(4):
for eighth in range(2):
notes.append(Note(
start=bar * 4 + beat + (eighth * 0.5),
duration=0.2,
velocity=velocity if eighth == 0 else velocity - 15,
pitch=DRUM_MAP["closed_hat"]
))
return Rhythm((4, 4), notes, bars * 4)
# =============================================================================
# MAIN GENERATOR
# =============================================================================
def generate_drum_pattern(
genre: str = "electronic",
bars: int = 4,
bpm: float = 120,
variation: str = "basic",
swing: float = 0.0
) -> DrumPattern:
"""
Generate a drum pattern for a specific genre.
Args:
genre: Genre (electronic, hiphop, rock, lofi, trap, etc.)
bars: Number of bars
bpm: Tempo
variation: Pattern variation (basic, complex, minimal, etc.)
swing: Swing amount (0.0 to 0.5)
Returns:
DrumPattern with all instrument tracks
"""
tracks = {}
genre = genre.lower()
if genre in ("electronic", "house", "techno"):
tracks["kick"] = _create_four_on_floor(bars)
tracks["snare"] = _create_backbeat_snare(bars, 90)
tracks["closed_hat"] = _create_eighth_hat(bars)
tracks["open_hat"] = _create_offbeat_hat(bars)
elif genre in ("hiphop", "hip-hop", "boom_bap", "lofi"):
tracks["kick"] = _create_boom_bap_kick(bars)
tracks["snare"] = _create_backbeat_snare(bars)
tracks["closed_hat"] = _create_eighth_hat(bars, 55)
swing = max(swing, 0.15) # Lo-fi needs swing
elif genre == "trap":
tracks["kick"] = _create_boom_bap_kick(bars)
tracks["snare"] = _create_backbeat_snare(bars, 110)
tracks["closed_hat"] = _create_trap_hihat(bars)
elif genre in ("rock", "punk", "emo"):
tracks["kick"] = _create_four_on_floor(bars, 110)
tracks["snare"] = _create_backbeat_snare(bars, 120)
tracks["closed_hat"] = _create_eighth_hat(bars, 75)
elif genre in ("chiptune", "8bit"):
# Simple, punchy patterns
tracks["kick"] = _create_four_on_floor(bars, 120)
tracks["snare"] = _create_backbeat_snare(bars, 110)
else:
# Default pattern
tracks["kick"] = _create_four_on_floor(bars)
tracks["snare"] = _create_backbeat_snare(bars)
tracks["closed_hat"] = _create_eighth_hat(bars)
# Apply swing if specified
if swing > 0:
for name, rhythm in tracks.items():
tracks[name] = rhythm.with_swing(swing)
return DrumPattern(
name=f"{genre}_{variation}",
bars=bars,
bpm=bpm,
time_signature=(4, 4),
tracks=tracks
)
