Sample n stands at a*n/d samples of rate, in lowest terms, a, d > 0: every grid
starts at t = 0, so a sample index is the one clock every read and key counts in.
Reader sample n reads source sample (a*n + b)/d, d > 0: exactly, or rounded down or
to the nearest, ties to even. An exact map is whole, d = 1; nothing reads between samples.
scale*t + shift + gain*((inner_scale*t + inner_shift) mod period) at sample n’s
instant, each a rational (num, den) with den > 0 and period > 0. The remainder and
the sum are integers over one denominator, so which side of a jump an instant falls on is
decided exactly and only the quotient that states the sum rounds.
Every closed form-typed subterm was collapsed to a buffer, inlined or held as a formula
before this tree was built, so there is no oscillator, no series and no delta here.