Two charts wired to 01-the-math. The left chart shows
60/BPM(b) — seconds per beat. The shaded area
under that curve from 0 to β is the elapsed-seconds value
on the right chart at the same β. That equality is the integral
t(β) = ∫0β 60/BPM(b) db.
60/BPM(b) — seconds per beat. The shaded area from 0
to β is the elapsed seconds on the right.
t(β). In piecewise mode, drag the
coloured dots to pin a beat to a new second.