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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)
kfco = p6
krez = p7
; Calculate the biquadratic filter's coefficients
kfcon = 2*3.14159265*kfco/sr
kalpha = 1-2*krez*cos(kfcon)*cos(kfcon)+krez*krez*cos(2*kfcon)
kbeta = krez*krez*sin(2*kfcon)-2*krez*cos(kfcon)*sin(kfcon)
kgama = 1+cos(kfcon)
km1 = kalpha*kgama+kbeta*sin(kfcon)
km2 = kalpha*kgama-kbeta*sin(kfcon)
kden = sqrt(km1*km1+km2*km2)
kb0 = 1.5*(kalpha*kalpha+kbeta*kbeta)/kden
kb1 = kb0
kb2 = 0
ka0 = 1
ka1 = -2*krez*cos(kfcon)
ka2 = krez*krez
; Generate an input signal.
axn vco 1, icps, 1
; Filter the input signal.
ayn biquad axn, kb0, kb1, kb2, ka0, ka1, ka2
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 Fco Rez
i 1 0.0 1.0 20000 6.00 1000 .8
i 1 1.0 1.0 20000 6.03 2000 .95
e
</CsScore>
</CsoundSynthesizer>
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