#lang scribble/manual
@(require (for-label racket))

@title{(allpass-n in maxDelayTime delayTime decayTime)}


All pass delay line. allpass-n uses no interpolation, allpass-l uses
linear interpolation, allpass-c uses all pass interpolation.  All
time values are in seconds.  The decay time is the time for the
echoes to decay by 60 decibels. If this time is negative then the
feedback coefficient will be negative, thus emphasizing only odd
harmonics at an octave lower.

Since the allpass delay has no audible effect as a resonator on
steady state sound ...


@racketblock[
(define z (mul (white-noise ar) 0.1))
]


@racketblock[
(audition (out 0 (allpass-c z 0.01 (x-line kr 0.0001 0.01 20 do-nothing) 0.2)))
]

...these examples add the input to the effected sound so that you
can hear the effect of the phase comb.


@racketblock[
(audition
 (out 0 (add z (allpass-n z 0.01 (x-line kr 0.0001 0.01 20 do-nothing) 0.2))))
]


@racketblock[
(audition
 (out 0 (add z (allpass-l z 0.01 (x-line kr 0.0001 0.01 20 do-nothing) 0.2))))
]


@racketblock[
(audition
 (out 0 (add z (allpass-c z 0.01 (x-line kr 0.0001 0.01 20 do-nothing) 0.2))))
]

Used as an echo - doesn't really sound different than Comb, but it
outputs the input signal immediately (inverted) and the echoes are
lower in amplitude.


@racketblock[
(audition
 (out 0 (allpass-n (mul (decay (dust ar 1) 0.2) z) 0.2 0.2 3)))
]