Deterministic, but unpredictable. Feed a simple rule back into itself — the logistic map xₙ₊₁ = r·xₙ·(1−xₙ) is the classic — and as you raise its one parameter it stops settling: a fixed point splits to period-2, then 4, 8, and by r ≈ 3.57 it's chaotic, wandering forever without repeating. Read that wandering as a waveform and you get a knob that sweeps continuously from pure tone to pure noise. The Hénon and Lorenz attractors do the same in more dimensions. No randomness anywhere — just nonlinearity folding back on itself.
For the logistic map: below 3 it's a tone, ~3–3.5 it buzzes with period-doubling, above ≈3.57 it turns to noise. (r applies to the logistic map.)
Rate is how fast the map iterates; the note you play scales it, so it's roughly pitched.
play a note (a s d f …) and sweep chaos (r) from tone to noise