A synthetic 10s click train at 120 BPM (5ms decaying 1kHz bursts every 0.5s, sr=22050) goes
through the canonical beat_track() and the explicit quick tier
quickTempo(). Proofs: tempo lands in one of the two lag bins bracketing 120 BPM
(117.45 / 123.05 at hop=512), 18–21 beats over 10s, median inter-beat interval within one
hop (23.2ms) of 0.500s, and quickTempo lands in the SAME lag bin with measured confidence
> 0. Orange ticks mark detected beats; the play button beeps on each detected beat so you can
hear the lock. Same asserts as examples/node/beat-tracker.mjs.