/patches/LivingstonGuitar
#! | 179 lines | 179 code | 0 blank | 0 comment | 0 complexity | 2362b7973c4bf21f08a8133fc78da0a3 MD5 | raw file
- instr LivingstonGuitar
- ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
- ; The model takes pluck position, and pickup position (in % of string length), and generates
- ; a pluck excitation signal, representing the string displacement. The pluck consists
- ; of a forward and backward traveling displacement wave, which are recirculated thru two
- ; separate delay lines, to simulate the one dimensional string waveguide, with
- ; fixed ends.
- ;
- ; Losses due to internal friction of the string, and with air, as well as
- ; losses due to the mechanical impedance of the string terminations are simulated by
- ; low pass filtering the signal inside the feedback loops.
- ; Delay line outputs at the bridge termination are summed and fed into an IIR filter
- ; modeled to simulate the lowest two vibrational modes (resonances) of the guitar body.
- ; The theory implies that force due to string displacement, which is equivalent to
- ; displacement velocity times bridge mechanical impedance, is the input to the guitar
- ; body resonator model. Here we have modified the transfer fuction representing the bridge
- ; mech impedance, to become the string displacement to bridge input force transfer function.
- ; The output of the resulting filter represents the displacement of the guitar's top plate,
- ; and sound hole, since thier respective displacement with be propotional to input force.
- ; (based on a simplified model, viewing the top plate as a force driven spring).
- ;
- ; The effects of pluck hardness, and contact with frets during pluck release,
- ; have been modeled by injecting noise into the initial pluck, proportional to initial
- ; string displacement.
- ;
- ; Note on pluck shape: Starting with a triangular displacment, I found a decent sounding
- ; initial pluck shape after some trial and error. This pluck shape, which is a linear
- ; ramp, with steep fall off, doesn't necessarily agree with the pluck string models I've
- ; studied. I found that initial pluck shape significantly affects the realism of the
- ; sound output, but I the treatment of this topic in musical acoustics literature seems
- ; rather limited as far as I've encountered.
- ;
- ; Original pfields
- ; p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12 p13
- ; in st dur amp pch plklen fbfac pkupPos pluckPos brightness vibf vibd vibdel
- ; i01.2 0.5 0.75 5000 7.11 .85 0.9975 .0 .25 1 0 0 0
- pset 0, 0, 3600, 0, 0, 0, 0, 0, 0, 0, 0
- iHz,kHz,iamplitude,idB NoteOn p4, p5, 13
- p3, adamping Damping 0.003, p3,.03
- ip4 init iamplitude
- ip6 init 0.85
- ip7 init 0.9975
- ip8 init 0
- ip9 init 0.25
- ip10 init 1.0
- ip11 init 0.001
- ip12 init 0.0
- ip13 init 0.0
- afwav init 0
- abkwav init 0
- abkdout init 0
- afwdout init 0
- iEstr init 1.0 / cpspch(6.04)
- ifqc init iHz ; cpspch(p5)
- ; note:delay time=2x length of string (time to traverse it)
- idlt init 1.0 / ifqc
- print iHz, ifqc, idlt
- ipluck = 0.5 * idlt * ip6 * ifqc / cpspch(8.02)
- ifbfac = ip7 ; feedback factor
- ; (exponentialy scaled) additive noise to add hi freq content
- ibrightness = ip10 * exp(ip6 * log(2)) / 2
- ivibRate = ip11
- ivibDepth pow 2, ip12 / 12
- ; vibrato depth, +,- ivibDepth semitones
- ivibDepth = idlt - 1.0 / (ivibDepth * ifqc)
- ; vibrato start delay (secs)
- ivibStDly = ip13
- ; termination impedance model
- ; cutoff freq of LPF due to mech. impedance at the nut (2kHz-10kHz)
- if0 = 10000
- ; damping parameter of nut impedance
- iA0 = ip7
- ialpha = cos(2 * 3.14159265 * if0 * 1 / sr)
- ; FIR LPF model of nut impedance, H(z)=a0+a1z^-1+a0z^-2
- ia0 = 0.3 * iA0 / (2 * (1 - ialpha))
- ia1 = iA0 - 2 * ia0
- ; NOTE each filter pass adds a sampling period delay,so subtract 1/sr from tap time to compensate
- ; determine (in crude fashion) which string is being played
- ; icurStr = (ifqc > cpspch(6.04) ? 2 : 1)
- ; icurStr = (ifqc > cpspch(6.09) ? 3 : icurStr)
- ; icurStr = (ifqc > cpspch(7.02) ? 4 : icurStr)
- ; icurStr = (ifqc > cpspch(7.07) ? 5 : icurStr)
- ; icurStr = (ifqc > cpspch(7.11) ? 6 : icurStr)
- ipupos = ip8 * idlt / 2 ; pick up position (in % of low E string length)
- ippos = ip9 * idlt / 2 ; pluck position (in % of low E string length)
- isegF = 1 / sr
- isegF2 = ipluck
- iplkdelF = (ipluck / 2 > ippos ? 0 : ippos - ipluck / 2)
- isegB = 1 / sr
- isegB2 = ipluck
- iplkdelB = (ipluck / 2 > idlt / 2 - ippos ? 0 : idlt / 2 - ippos - ipluck / 2)
- ; EXCITATION SIGNAL GENERATION
- ; the two excitation signals are fed into the fwd delay represent the 1st and 2nd
- ; reflections off of the left boundary, and two accelerations fed into the bkwd delay
- ; represent the the 1st and 2nd reflections off of the right boundary.
- ; Likewise for the backward traveling acceleration waves, only they encouter the
- ; terminationsin the opposite order.
- ipw = 1
- ipamp = ip4 * ipluck ; 4 / ipluck
- aenvstrf linseg 0, isegF, -ipamp / 2, isegF2, 0
- adel1 delayr (idlt > 0) ? idlt : 0.01
- ; initial forward traveling wave (pluck to bridge)
- aenvstrf1 deltapi iplkdelF
- ; first forward traveling reflection (nut to bridge)
- aenvstrf2 deltapi iplkdelB + idlt / 2
- delayw aenvstrf
- ; inject noise for attack time string fret contact, and pre pluck vibrations against pick
- anoiz rand ibrightness
- aenvstrf1 = aenvstrf1 + anoiz*aenvstrf1
- aenvstrf2 = aenvstrf2 + anoiz*aenvstrf2
- ; filter to account for losses along loop path
- aenvstrf2 filter2 aenvstrf2, 3, 0, ia0, ia1, ia0
- ; combine into one signal (flip refl wave's phase)
- aenvstrf = aenvstrf1 - aenvstrf2
- ; initial backward excitation wave
- aenvstrb linseg 0, isegB, - ipamp / 2, isegB2, 0
- adel2 delayr (idlt > 0) ? idlt : 0.01
- ; initial bdwd traveling wave (pluck to nut)
- aenvstrb1 deltapi iplkdelB
- ; first forward traveling reflection (nut to bridge)
- aenvstrb2 deltapi idlt / 2 + iplkdelF
- delayw aenvstrb
- ; initial bdwd traveling wave (pluck to nut)
- ; aenvstrb1 delay aenvstrb, iplkdelB
- ; first bkwd traveling reflection (bridge to nut)
- ; aenvstrb2 delay aenvstrb, idlt/2+iplkdelF
- ; inject noise
- aenvstrb1 = aenvstrb1 + anoiz*aenvstrb1
- aenvstrb2 = aenvstrb2 + anoiz*aenvstrb2
- ; filter to account for losses along loop path
- aenvstrb2 filter2 aenvstrb2, 3, 0, ia0, ia1, ia0
- ; combine into one signal (flip refl wave's phase)
- aenvstrb = aenvstrb1 - aenvstrb2
- ; low pass to band limit initial accel signals to be < 1/2 the sampling freq
- ainputf tone aenvstrf, sr * 0.9 / 2
- ainputb tone aenvstrb, sr * 0.9 / 2
- ; additional lowpass filtering for pluck shaping\
- ; Note, it would be more efficient to combine stages into a single filter
- ainputf tone ainputf, sr * 0.9 / 2
- ainputb tone ainputb, sr * 0.9 / 2
- ; Vibrato generator
- icosine ftgenonce 0, 0, 65537, 11, 1.0
- avib poscil ivibDepth, ivibRate, icosine
- avibdl delayr (((ivibStDly * 1.1)) > 0.0) ? (ivibStDly * 1.1) : 0.01
- avibrato deltapi ivibStDly
- delayw avib
- ; Dual Delay line,
- ; NOTE: delay length longer than needed by a bit so that the output at t=idlt will be interpolated properly
- ;forward traveling wave delay line
- afd delayr (((idlt + ivibDepth) * 1.1) > 0.0) ? ((idlt + ivibDepth) * 1.1) : 0.01
- ; output tap point for fwd traveling wave
- afwav deltapi ipupos
- ; output at end of fwd delay (left string boundary)
- afwdout deltapi idlt - 1 / sr + avibrato
- ; lpf/attn due to reflection impedance
- afwdout filter2 afwdout, 3, 0, ia0, ia1, ia0
- delayw ainputf + afwdout * ifbfac * ifbfac
- ; backward trav wave delay line
- abkwd delayr (((idlt + ivibDepth) * 1.1) > 0) ? ((idlt + ivibDepth) * 1.1) : 0.01
- ; output tap point for bkwd traveling wave
- abkwav deltapi idlt / 2 - ipupos
- ; output at the left boundary
- ; abkterm deltapi idlt/2
- ; output at end of bkwd delay (right string boundary)
- abkdout deltapi idlt - 1 / sr + avibrato
- abkdout filter2 abkdout, 3, 0, ia0, ia1, ia0
- delayw ainputb + abkdout * ifbfac * ifbfac
- ; resonant body filter model, from Cuzzucoli and Lombardo
- ; IIR filter derived via bilinear transform method
- ; the theoretical resonances resulting from circuit model should be:
- ; resonance due to the air volume + soundhole = 110Hz (strongest)
- ; resonance due to the top plate = 220Hz
- ; resonance due to the inclusion of the back plate = 400Hz (weakest)
- aresbod filter2 (afwdout + abkdout), 5, 4, 0.000000000005398681501844749, .00000000000001421085471520200, -.00000000001076383426834582, -00000000000001110223024625157, .000000000005392353230604385, -3.990098622573566, 5.974971737738533, -3.979630684599723, .9947612723736902
- asig = (1500 * (afwav + abkwav + aresbod * .000000000000000000003)) * adamping
- aleft, aright Pan p7, asig
- outleta "leftout", aleft
- outleta "rightout", aright
- endin