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<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 biquad.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>
; Initialize the global variables.
sr = 44100
kr = 4410
ksmps = 10
nchnls = 2
; Instrument #1.
instr 1
; Get the values from the score.
idur = p3
iamp = p4
icps = cpspch(p5)
afco expon 100, p3, 2000
arez line 0.8, p3, 0.99
; Calculate the biquadratic filter's coefficients
afcon = 2*3.14159265*afco/sr
aalpha = 1-2*arez*cos(afcon)*cos(afcon)+arez*arez*cos(2*afcon)
abeta = arez*arez*sin(2*afcon)-2*arez*cos(afcon)*sin(afcon)
agama = 1+cos(afcon)
am1 = aalpha*agama+abeta*sin(afcon)
am2 = aalpha*agama-abeta*sin(afcon)
aden = sqrt(am1*am1+am2*am2)
ab0 = 1.5*(aalpha*aalpha+abeta*abeta)/aden
ab1 = ab0
ab2 = 0
aa0 = 1
aa1 = -2*arez*cos(afcon)
aa2 = arez*arez
; Generate an input signal.
axn vco 1, icps, 1
; Filter the input signal.
ayn biquada axn, ab0, ab1, ab2, aa0, aa1, aa2
outs ayn*iamp/2, ayn*iamp/2
endin
</CsInstruments>
<CsScore>
; Table #1, a sine wave.
f 1 0 16384 10 1
; Sta Dur Amp Pitch
i 1 0.0 5.0 20000 6.00
e
</CsScore>
</CsoundSynthesizer>
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