Polyrhythm
3 against 2 · African drumming · LCM alignment
Physics: Polyrhythm N:M — the two cycles meet every LCM(N,M) beats. 3:2 = sesquialtera (3 notes in the time of 2). 4:3 common in Baroque hemiola (Handel). African polyrhythm: each individual part is simple, but the composite texture is complex. Ligeti's piano études use polyrhythm to create the illusion of faster tempo. Steve Reich's phasing: two identical loops drift apart by ~0.1% tempo difference. Human motor coordination: 1:1, 1:2, 3:2 are natural ratio attractors (Haken-Kelso-Bunz model, 1985).