mvclpf2 — Moog voltage-controlled lowpass filter emulation.


Mvclpf2 is an digital implementation of the 4th-order (24 dB/oct) Moog ladder filter originally written by Fons Andriaensen. According to the author, mvclpf2 "uses five non-linear elements, in the input and in all four filter sections. It works by using the derivative of the nonlinearity (for which 1 / (1 + x * x) is reasonable approximation). The main advantage of this is that only one evaluation of the non-linear function is required for each section".


asig mvclpf2 ain, xcf, xres[, istor]


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.


ain -- input signal.

xcf -- filter cutoff frequency. The useful range is around six octaves below and above middle C (pch 8.00).

xres -- resonance, limited to the interval [0,1].


Here is an example of the mvclpf2 opcode. It uses the file mvclpf2.csd.

Example 663. Example of the mvclpf2 opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

0dbfs = 1

instr 1
 kenv linen p4,0.1,p3,0.1
 ain rand kenv 
 kfr expon 220, p3, 1760
 asig mvclpf1 ain,kfr,0.9
   out asig

i1 0 5 0.9

See also

Standard Filters: Resonant Low-pass filters


Author: Fons Andriaensen,
ported to Csound by Victor Lazzarini
January 2016

New in version 6.07

January 2016.