mode
mode — A filter that simulates a mass-spring-damper system
Description
Filters the incoming signal with the specified resonance frequency and quality factor. It can also be seen as a signal generator for high quality factor, with an impulse for the excitation. You can combine several modes to built complex instruments such as bells or guitar tables.
Performance
aout -- filtered signal
ain -- signal to filter
xfreq -- resonant frequency of the filter
![[Warning]](images/warning.png)
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Warning |
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As this filter would become unstable if sr/xfreq < pi, the value of the xfreq is limited to sr/pi-sr/100 internally (e.g xfreq > 13596 Hz @ 44.1 kHz). The sr/100 term is because the filter while mathematically stable has a very large amplification as it approaches the unstable region. |
xQ -- quality factor of the filter
The resonance time is roughly proportional to xQ/xfreq.
See Modal Frequency Ratios for frequency ratios of real instruments which can be used to determine the values of xfreq.
Examples
Here is an example of the mode opcode. It uses the file mode.csd.
Example 629. Example of the mode opcode.
See the sections Real-time Audio and Command Line Flags for more information on using command line flags.
<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 = 2 instr 1; 2 modes excitator idur init p3 ifreq11 init p4 ifreq12 init p5 iQ11 init p6 iQ12 init p7 iamp init ampdb(p8) ifreq21 init p9 ifreq22 init p10 iQ21 init p11 iQ22 init p12 ; to simulate the shock between the excitator and the resonator ashock mpulse 3,0 aexc1 mode ashock,ifreq11,iQ11 aexc1 = aexc1*iamp aexc2 mode ashock,ifreq12,iQ12 aexc2 = aexc2*iamp aexc = (aexc1+aexc2)/2 ;"Contact" condition : when aexc reaches 0, the excitator looses ;contact with the resonator, and stops "pushing it" aexc limit aexc,0,3*iamp ; 2modes resonator ares1 mode aexc,ifreq21,iQ21 ares2 mode aexc,ifreq22,iQ22 ares = (ares1+ares2)/2 display aexc+ares,p3 outs aexc+ares,aexc+ares endin </CsInstruments> <CsScore> ;wooden excitator against glass resonator i1 0 8 1000 3000 12 8 70 440 888 500 420 ;felt against glass i1 4 8 80 188 8 3 70 440 888 500 420 ;wood against wood i1 8 8 1000 3000 12 8 70 440 630 60 53 ;felt against wood i1 12 8 80 180 8 3 70 440 630 60 53 i1 16 8 1000 3000 12 8 70 440 888 2000 1630 i1 23 8 80 180 8 3 70 440 888 2000 1630 ;With a metallic excitator i1 33 8 1000 1800 1000 720 70 440 882 500 500 i1 37 8 1000 1800 1000 850 70 440 630 60 53 i1 42 8 1000 1800 2000 1720 70 440 442 500 500 </CsScore> </CsoundSynthesizer>