source.loop proof
A seamless loop should just spin: no click, no gap, the bassline coming
back around at exactly the same spot every pass. Press Play to
hear a 2.6-second bass loop repeat while the page listens to its own
output and verifies the cycle really lands where it claims. Technically
it loads Bassline For Doppler Song longer.wav and plays the golden
loop (11.9886 s → 14.6008 s, cycle 2.6122 s) via LoopPlayer's native
source.loop: (1) the suspended AudioContext must resume
inside play(); (2) setVolume(0.1) must land on the gain node; (3) an
AnalyserNode taps the source and records the RMS energy envelope for
~9 s (3+ cycles) — the envelope's autocorrelation peak (the recurring
loop-start energy fingerprint) must sit at the loop period 2.612 s
±20 ms, proving native looping honors the exact points.