A DelayVar is the graph's memory primitive: a ring buffer with one writer
and any number of readers. Everything stateful — one-sample feedback, filters,
envelopes, comb delays, phase accumulators, counters — is built on it.
| Function | Description |
|---|---|
delayVar() | Declare a delay line. Its length is inferred from the largest fixed read index. |
delayVar(maxDelay) | Declare a delay line sized for variable reads: maxDelay is the maximum delay in samples (an AsSignal; usually maxSeconds * fs()). |
d <- x / x -> d / d write(x) | Write x into the line (once per sample). Returns x, so a write can sit inside an expression. Each delay has exactly one writer. |
d read(n) / d at(n) / d(n) | Read the value written n samples ago (fixed integer n). d(1) is the previous sample's write — a unit delay. d(0) (or d()) reads the value written this sample. |
d vread(index, interp = Interpolation.cubic) / d(indexSignal) | Variable (modulated) read at a signal-valued delay in samples, with interpolation. Requires delayVar(maxDelay). |
d init(n, x) | Set the initial content at offset n (evaluated at init rate), so the first reads see x instead of 0. |
Interpolation for variable reads:
Interpolation.none (nearest), linear (2-point),
cubic (4-point), lagrange (8-point), sinc
(8-point).
Reads at index ≥ 1 see previous samples, so a delay can be read and written in the same graph — that is how feedback works. The canonical one-pole filter:
fn onepole(x S, a AsSignal) S {
let y = delayVar();
y <- x + a * (y(1) - x) -- y[n] = x + a*(y[n-1] - x); the write is the result
}Since write returns the written value, the whole function body is both "update
the state" and "the output". The unit-delay ugens z1 / z2
(§15.11) package the common cases: x z1 is
x delayed one sample.
A delay declared with a multichannel writer widens per channel — each channel gets
its own line. Delay times in seconds must be converted:
delayTime * fs() is the read index in samples (see comb in
§15.14 for the full pattern).
-- variable-delay chorus voice: 0..10 ms modulated cubic read
fn chorusTap(x S, rate AsSignal) S {
let maxSamps = 0.01 * fs();
let d = delayVar(maxSamps);
d <- x;
d(rate sinosc uni * maxSamps) -- d(S) = vread, cubic by default
}