Delays and reverbs

A delay stores earlier samples; feedback writes part of the delayed signal back into the line. Reverb combines delays, filters and diffusion into a tail. The toolkit offers small line primitives and complete stereo structures so you can choose the amount of composition your product needs.

Choose the time structure

Need	Start with	Why
Exact parallel alignment	delays/alignment	Whole frames, no interpolation, clipping or feedback.
Short movable read time	delays/fractional	Fractional reads for modulation; prepare capacity first.
Repeating echo	delays/feedback, delays/saturated-feedback	Explicit regeneration, with optional coloured feedback.
Alternating stereo repeats	delays/ping-pong, delays/cross-feed	Choose strict alternating repeats or flexible cross-feed.
Rhythmic taps or reverse windows	delays/tap-pattern, delays/reverse-delay	Prepared rings plus the selected tap/window policy.
Algorithmic space	reverbs/stereo-room-fdn, reverbs/stereo-dattorro, reverbs/stereo-schroeder	Stereo adapters with defined decay, predelay and control behavior.
Convolution room	acoustics/room-convolver	Play a prepared IR; see room acoustics.

Storage and live changes

Prepare the maximum delay storage outside rendering. Read delay in samples or milliseconds according to the setter; convert tempo divisions with control/musical-clock. A nominal “delay” control is not a universal unit. The basic fractional-delay leaf caps its non-feedback line at 50 ms and its fractional-feedback line at 1000 ms; select another owner for a larger capacity.

Changing a read position immediately can click or change pitch. Use the leaf’s slew, dual-read crossfade or staged transition where appropriate. Clearing a large ring during a callback creates a work spike: use the staged-clear API for live transitions, with a bounded shared budget.

Leaves named borrowed-* and several tap/pitch algorithms use caller-owned rings. Their scalar reset and storage clear must happen together. A hall needs at least sampleRate + two frames per borrowed ring; other leaves have their own requirements. Do not assume that all delay/reverb APIs allocate their own storage or mix in dry audio. True ping-pong and the stereo reverb adapters listed as wet-only need an explicit product mix.

Check tails and parallel paths

Decide whether bypass preserves a tail, fades it or clears it. Test feedback, maximum decay and repeated changes for finite output and adequate headroom. Use exact alignment for delayed parallel dry/wet paths, and check Haas widening in mono. A decay parameter describes the algorithm’s law; it does not establish that the result reproduces a measured room or spring tank.

Toolkit reference

Import paths below are suffixes of maruaudio/dsp/. Use the exported types and setters in your installed version for complete signatures and defaults.

Delays

Import suffix	Purpose	Selected API
delays/cross-feed	Stereo delay with same-side/cross-side feedback, tone filtering, modulation, read-time crossfades and feedback saturation.	initCrossFeedDelayNode, crossFeedDelayNodeTick
delays/fractional	Fractional delay and feedback delay with linear interpolation and prepared ring storage.	initFractionalFeedbackDelayNode, fractionalFeedbackDelayNodeTick
delays/saturated-feedback	Tape-style feedback delay with damping, soft clipping and dry/wet mixing.	initSaturatedFeedbackDelayNode, saturatedFeedbackDelayNodeTick
delays/ping-pong	True ping-pong delay: two cross-feeding fixed lines producing structurally alternating L/R repeats, 100% wet.	initPingPongDelayNode, setPingPongFeedback
delays/primitives	Milliseconds-to-frames, dry/wet and bounded feedback-write helpers.	delayFrameCount, delayDryWetMix
delays/feedback	Fixed feedback delay over a prepared line with a bounded active length.	initFeedbackDelayNode, feedbackDelayNodeTick
delays/bounded	Non-regenerating fixed delay: the feedback delay's sibling, writing through the same bounded store with the regeneration term exactly zero so all three delay behaviors share one implementation.	initBoundedDelayNode, boundedDelayNodeTick
delays/alignment	Exact whole-frame alignment without clipping, interpolation or feedback; preserves over-unity dry carriers for parallel effects.	initAlignmentDelay, alignmentDelayTick
delays/pcm16-interpolated	Firmware-derived stereo delay with PCM16 storage and interpolated reads.	initPcm16InterpolatedDelay, pcm16InterpolatedDelayTickWritePointer
delays/pcm16-ping-pong	Firmware-derived PCM16 ping-pong delay with glided time/feedback and its variant-specific dry/wet law.	initPcm16PingPongNode, pcm16PingPongNodeTick
delays/clocked-glitch	Clocked stereo delay with seeded retrigger/reverse/pitch/pan changes, crossfades and a frozen-loop buffer.	initClockedGlitchDelay, clockedGlitchDelayTick
delays/tap-pattern	Four-tap, Haas and damped feedback-comb compositions over caller-owned stereo rings.	initTapPattern, tapPatternTick
delays/reverse-delay	Windowed reverse delay over caller-owned stereo rings with edge fades.	initReverseDelay, reverseDelayTick

Reverbs

Import suffix	Purpose	Selected API
reverbs/schroeder	Four-comb/two-allpass Schroeder/Freeverb network with damping and full-tail reset.	initReverbNode, reverbNodeTick
reverbs/dattorro	True-stereo Dattorro diffusion/tank reverb.	initDattorroNode, dattorroNodeTick
reverbs/stereo-room-fdn	Wet-only stereo four-line FDN with physical decay time, live room-size slew and bounded staged clearing.	initStereoRoomFdnNode, stereoRoomFdnNodeTick
reverbs/stereo-dattorro	Wet-only Dattorro adapter with bounded live predelay and normalized decay/damping controls.	initStereoDattorroNode, stereoDattorroNodeTick
reverbs/stereo-schroeder	Wet-only dual-core Schroeder adapter with explicit right-channel decorrelation and bounded live predelay.	initStereoSchroederNode, stereoSchroederNodeTick
reverbs/griesinger	Firmware-derived Griesinger figure-eight reverb with input diffusion, selectable storage precision and a freeze variant.	initGriesingerReverb, griesingerReverbTick
reverbs/borrowed-spring	Dispersive spring-style waveguide with coupled caller-owned delay loops.	initBorrowedSpring, borrowedSpringTick
reverbs/borrowed-hall-fdn	Hall feedback-delay network over caller-owned delay storage.	initBorrowedHallFdn, borrowedHallFdnTick

Return to DSP fundamentals for I/O, lifecycle, units and the category map.