Description

A digital emulation of the Moog diode ladder filter configuration.

Syntax

ares moogvcf2 asig, xfco, xres [,iscale, iskip]

Initialization

iscale (optional, default=0dBfs) -- internal scaling factor, as the operation of the code requires the signal to be in the range +/-1. Input is first divided by iscale, then output is mutliplied by iscale.

iskip (optional, default=0) -- if non zero skip the initialisation of the filter.

Performance

asig -- input signal

xfco -- filter cut-off frequency in Hz. which may be i-,k-, or a-rate.

xres -- amount of resonance. Self-oscillation occurs when xres is approximately one. May be a-rate, i-rate, or k-rate.

moogvcf2 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 and then adjusted.

moogvcf2 is identical to moogvcf, except that the

Examples

Here is an example of the moogvcf2 opcode. It uses the file moogvcf2.csd.

<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
; Audio out   Audio in    No messages
-odac           -iadc     -d     ;;;RT audio I/O
; For Non-realtime ouput leave only the line below:
; -o moogvcf.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

; 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

  a1 moogvcf2 asig, kfco, krez

  out a1
endin


</CsInstruments>
<CsScore>

; 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


</CsScore>
</CsoundSynthesizer>

See Also

moogvcf, biquad, rezzy

Credits

Example written by Kevin Conder.

New in Csound version 5.03