moogladder2

Moog ladder lowpass filter.

Moogladder2 is an new digital implementation of the Moog ladder filter based on the work of Antti Huovilainen, described in the paper "Non-Linear Digital Implementation of the Moog Ladder Filter" (Proceedings of DaFX04, Univ of Napoli). This implementation uses approximations to the tanh function and so is faster but less accurate than moogladder.

Syntax

asig moogladder2 ain, kcf, kres[, istor]
asig moogladder2 ain, acf, kres[, istor]
asig moogladder2 ain, kcf, ares[, istor]
asig moogladder2 ain, acf, ares[, istor]

Initialization

istor --initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0.

Performance

asig -- input signal.

kcf/acf -- filter cutoff frequency

kres/ares -- resonance, generally < 1, but not limited to it. Higher than 1 resonance values might cause aliasing, analogue synths generally allow resonances to be above 1.

Examples

Here is an example of the moogladder2 opcode. It uses the file moogladder2.csd.

<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac   ;;;realtime audio out
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o moogladder2.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

instr 1

kfe  expseg 500, p3*0.9, 1800, p3*0.1, 3000
asig buzz  1, 100, 20, 1
kres line .1, p3, .99   ;increase resonance
afil moogladder2 asig, kfe, kres
     outs afil, afil

endin
</CsInstruments>
<CsScore>
f 1 0 4096 10 1

i 1 0 10
e
</CsScore>
</CsoundSynthesizer>

See also

Standard Filters: Resonant Low-pass filters

Credits

Author: Victor Lazzarini
Author: John ffitch
April 2016

New in version 6.07