Design: Ensemble Groove

Problem

Per-instrument rhythm with a single swing parameter is not groove. Groove is the ensemble-wide microtiming and velocity feel that makes music breathe.

Solution

GrooveProfile as a frozen dataclass applied to all instruments via GrooveApplicator.

GrooveProfile Fields

Field	Type	Description
microtiming	dict[int, float]	16th-note position (0–15) → ms offset [-50, 50]
velocity_pattern	dict[int, float]	16th position → velocity multiplier
ghost_probability	float	[0, 1] — chance of ghost notes
swing_ratio	float	0.5 = straight, 0.667 = triplet swing
timing_jitter_sigma	float	ms σ for humanization
apply_to_all_instruments	bool	False restricts groove to drums only

Pipeline Position

Note Realizer → DynamicsShape → GrooveApplicator → Humanize → MIDI Write

Library

20 genre profiles in grooves/*.yaml. Loaded via load_groove(name):

jazz_swing, bossa_nova, funk_16th, lofi_hiphop, edm_4onfloor, reggae_one_drop, trap_double_time, rock_backbeat, pop_straight, j_pop_tight, ambient_fluid, cinematic_legato, waltz_viennese, shuffle_blues, samba, afrobeat, new_orleans_second_line, drum_n_bass, flamenco_bulerias, bollywood_filmi

Critique Rules

• groove_inconsistency: groove-dependent genre with no groove applied
• microtiming_flatness: all hits at zero microtiming in long pieces
• ensemble_groove_conflict: swing mismatch with genre expectations

Files

• src/yao/ir/groove.py — GrooveProfile
• src/yao/generators/groove_applicator.py — apply_groove()
• src/yao/schema/groove.py — GrooveSpec
• src/yao/verify/critique/groove_rules.py — 3 critique rules
• grooves/*.yaml — 20 groove definitions