tap

A single delay tap, used with with_taps to build discrete reflection-style reverb tails.

Signature

tap(delay_s, gain) -> Tap          // default decay (~80 ms 1/e)
tap(delay_s, gain, decay_k) -> Tap // explicit decay

signal.with_taps([tap_a, tap_b, ...]) -> Signal

A Tap is a (delay_s, gain, decay_k) triple. with_taps copies the source into the buffer at each tap’s offset, scaled by gain, then applies an independent exponential envelope per tap shaped by decay_k. The output extends past the source by the longest tap so the tail has somewhere to live.

What decay_k does

decay_k is the per-sample exponential decay rate measured against the tap’s own onset. The tap envelope at time t after onset is exp(-t × decay_k).

If you want sustained delayed copies of the source — the old behaviour — pass tap(delay, gain, 0). If you want reflections, the two-argument form does the right thing.

Why discrete decays, not convolution reverb

A real reverb convolves the source with the room’s impulse response. That’s expensive (FFT-domain or 5000+ taps) and overkill for a game-shaped reverb tail. Six decaying taps render in microseconds and give the “near reflections then late tail” character listeners expect.

A proper convolution reverb will land later when the recipes need it (probably for cathedral / open-ocean sounds). For sonar-room geometry, discrete reflection-style taps are the right tool.

Example

patch("sonar_ping", "one_shot",
    sine(330.0, 1.5).env(0.008, 1.4).gain(0.32)
        .with_taps([
            tap(0.13, 0.7),    // close, loud, brief
            tap(0.31, 0.5),    // mid, slightly quieter
            tap(0.58, 0.35),   // farther, quieter still
            tap(0.95, 0.22),   // distant late reflection
        ]));

That’s the submarine ping: a sine body with four reflections, each later and quieter, each itself brief (default 80 ms decay).

Errors

• with_taps: element N is not a Tap — one of the array elements wasn’t built with tap(...).

Notes

• Combining decays: a single signal can have many taps with different decay_k values — short close reflections plus a long diffused tail.
• Streaming caveat: in ambient patches the runtime delay-line uses a fixed per-tap gain (the decay_k field is ignored). The full exponential-decay shaping only applies in one-shot patches where the taps are baked into a finite buffer at eval time. Adding per-tap onset envelopes to the streaming delay line is a future change.