iscale (optional, default=1) -- internal scaling factor. Use if asig is not in the range +/-1. Input is first divided by iscale, then output is mutliplied iscale. Default value is 1. (New in Csound version 3.50)
asig -- input signal
xfco -- filter cut-off frequency in Hz. As of version 3.50, may i-,k-, or a-rate.
xres -- amount of resonance. Self-oscillation occurs when xres is approximately one. As of version 3.50, may a-rate, i-rate, or k-rate.
moogvcf is a digital emulation of the Moog diode ladder filter configuration. This emulation is based loosely on the paper "Analyzing the Moog VCF with Considerations for Digital Implemnetation" by Stilson and Smith (CCRMA). This version was originally coded in Csound by Josep Comajuncosas. Some modifications and conversion to C were done by Hans Mikelson
Note: This filter requires that the input signal be normalized to one.
Here is an example of the moogvcf opcode. It uses the files moogvcf.orc and moogvcf.sco.
Example 1. Example of the moogvcf opcode.
/* moogvcf.orc */
/* Written by Kevin Conder */
; Initialize the global variables.
sr = 44100
kr = 4410
ksmps = 10
nchnls = 1
; Instrument #1.
instr 1
; Use a nice sawtooth waveform.
asig vco 32000, 220, 1
; Vary the filter-cutoff frequency from .2 to 2 KHz.
kfco line 200, p3, 2000
; Set the resonance amount to one.
krez init 1
; Scale the amplitude to 32768.
iscale = 32768
a1 moogvcf asig, kfco, krez, iscale
out a1
endin
/* moogvcf.orc */
/* moogvcf.sco */
/* Written by Kevin Conder */
; Table #1, a sine wave for the vco opcode.
f 1 0 16384 10 1
; Play Instrument #1 for three seconds.
i 1 0 3
e
/* moogvcf.sco */