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scanu2

Compute the waveform and the wavetable for use in scanned synthesis.

Plugin opcode in scansyn.

Syntax

scanu2(init, irate, ifndisplace,ifnmass, ifnmatrix, ifncentr, ifndamp, \
       kmass, kmtrxstiff, kcentr, kdamp, ileft, iright, kpos, kdisplace, \
       ain, idisp, id)

scanu2 init, irate, ifndisplace,ifnmass, ifnmatrix, ifncentr, ifndamp, \
       kmass, kmtrxstiff, kcentr, kdamp, ileft, iright, kpos, kdisplace, \
       ain, idisp, id

Initialization

init -- the initial position of the masses. If this is a negative number, then the absolute of init signifies the table to use as a hammer shape. If init > 0, the length of it should be the same as the intended mass number, otherwise it can be anything. If init is not an integer the initial state is white noise with the fractional part being a scaling..

irate -- the amount of time between successive updates of the mass state. Kind of like the sample period of the system. If the number is big, the string will update at a slow rate showing little timbral variability; otherwise it will change rapidly resulting in a more dynamic sound.

ifndisplace -- the ftable that contains the initial velocity for each mass. It should have the same size as the intended mass number.

ifnmass -- ftable that contains the mass of each mass. It should have the same size as the intended mass number.

ifnmatrix -- ftable that contains the spring stiffness of each connection. It should have the same size as the square of the intended mass number. The data ordering is a row after row dump of the connection matrix of the system.

ifncentr -- ftable that contains the centering force of each mass. It should have the same size as the intended mass number.

ifndamp -- the ftable that contains the damping factor of each mass. It should have the same size as the intended mass number.

ileft -- If init < 0, the position of the positive pluck in the range 0 to 1. Ignored when init > 0.

iright -- If init < 0, the position of the negative pluck in the range 0 to 1. Ignored when init > 0.

If ileft is the same as iright a single positive pluck is used as initial state.

idisp -- If 0, no display of the masses is provided.

id -- If positive, the ID of the opcode. This will be used to point the scanning opcode to the proper waveform maker. If this value is negative, the absolute of this value is the wavetable on which to write the waveshape. That wavetable can be used later from an other opcode to generate sound. The initial contents of this table will be destroyed.

Performance

kmass -- scales the masses

kmtrxstiff -- scales the spring stiffness. Note that larger numbers slow the evolution of the vibration, which is the reciprocal of the coresponding parameter in scanu.

kcentr -- scales the centering force

kdamp -- scales the damping

kpos -- position of an active hammer along the string (kpos = 0 is leftmost, kpos = 1 is rightmost). The shape of the hammer is determined by init and the power it pushes with is kdisplace.

kdisplace -- power that the active hammer uses.

ain -- audio input that adds to the velocity of the masses. Amplitude should not be too great.

📝 Note

Both scanu and scanu2 are capable of reading the binary (.matrxB) and text (.matrxT) matrix format. However, using scanu2 is to be preferred because of its accuracy and better sound quality.

Examples

Here is an example of the scanu2 opcode. It uses the file scanu2.csd.

Example of the scanu2 opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac  --limiter=0.95 ;;;realtime audio out & and limit loud sounds
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o scanu2.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

; by Menno Knevel 2024

instr 1 

a0 init 0                                                                       ; no audio injection
irate = .01
kenv adsr  .0001,  1,  .7,  .1                                                  ; envelope

if (p6 == 1) then
    prints  "\ninitial displacement condition = ramp"
elseif (p6 == 11) then
    prints  "\ninitial displacement condition = sine (hammer???)"
else
    prints  "\ninitial displacement condition = a pluck that is 10 points wide on the surface"
endif

if (p7 == 3) then
    prints  "\n                                 (binary matrix)\n\n"
else
    prints  "\n                                 (text matrix)\n\n"
endif

; scanu init, irate, ifndisplace, ifnmass, ifnmatrix, ifncentr, ifndamp, kmass,
;       kmtrxstiff, kcentr, kdamp, ileft, iright, kpos, kdisplace, ain, idisp, id
scanu2 p6, irate, 6, 2, p7, 4, 5, 2, 9, .01, .01, .1, .9, 0, 0, a0, 1, 2

;ar scans kamp, kfreq, ifntraj, id
asig scans ampdb(p4)*kenv, cpspch(p5), 7, 2
outs asig*.00004, asig*.00004                                                   ; lower volume due to 0dbfs=1
        endin

</CsInstruments>
<CsScore>
; Initial displacement condition
f1 0 128 -7 0 64 1 64 0 ; ramp
f11 0 128 10 1 ; sine hammer
f111 0 128 -7 0 28 0 2 1 2 0 96 0 ; a pluck that is 10 points wide on the surface

; Masses
f2 0 128 -7 1 128 1

; Spring matrices
f3 0 16384 -23 "string-128.matrxB"
f33 0 16384 -44 "cylinder_128.matrxT"

; Centering force
f4 0 128 -7 1 128 1 ; uniform initial centering
; 0 128 -7 .001 128 1 ; ramped centering

; Damping
f5 0 128 -7 1 128 1 ; uniform damping

; Initial velocity - (displacement, vel, and acceleration
; Acceleration is from stiffness matrix pos effect - increases acceleration
f6 0 128 -7 .01 128 .01 ; uniform initial velocity

; exponential Trajectory
f7 0 128 -5 .001 128 128

i1 0  6 88      7.00    1       3
i1 7  2 88      5.00    1       3
i1 9  2 88      6.00    1       3

i1 12 6 86      7.00    11      3
i1 19 2 86      5.00    11      3
i1 21 2 86      6.00    11      3

i1 24 6 90      7.00    111     3
i1 31 2 90      5.00    111     3
i1 33 2 90      6.00    111     3

i1 37 6 88      7.00    1       33
i1 44 2 88      5.00    1       33
i1 46 2 88      6.00    1       33

i1 49 6 85      7.00    11      33
i 156 2 85      5.00    11      33
i1 58 2 85      6.00    11      33

i1 61 6 92      7.00    111     33
i1 68 2 92      5.00    111     33
i1 70 2 92      6.00    111     33
e
</CsScore>
</CsoundSynthesizer>

Here is another example of the scanu2 opcode. It uses the file scanu2-2.csd.

Second example of the scanu2 opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac  --limiter=0.95 ;;;realtime audio out & and limit loud sounds
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o scanu2-2.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

; by Menno Knevel 2024

instr 1 ; play with k-rate parameters

a0 init 0
irate = .2

kmass   line    10,  p3, 1
kstiff  line    .30, p3, .7
kcenter line    .3,  p3, .01
kdamp   line    -.01, p3, -.1
kdisplace line   0,  p3,  1

scanu2 1, irate, 6, 2, 3, 4, 5, kmass, kstiff, kcenter, kdamp, .1, .7, 1, kdisplace, a0, 1, 5
asig scans ampdbfs(p4), cpspch(p5), 7, 5
asig dcblock2 asig
asigL, asigR    reverbsc asig, asig, .6, 10000, sr, .5, 1  ; add some reverb
outs asigL+asig, asigR+asig
endin

</CsInstruments>
<CsScore>
; Initial displacement condition
f1 0 1024 10 1                  ; sine
f2 0 1024 -7 1 1024 1           ; Masses
; Spring text matrix
f3 0  0   -44  "circularstring_1024.matrxT"    ; text matrix, to be found in manual/examples
f4 0 1024 -7 1 1024 1 ; uniform initial centering
f5 0 1024 -7 1 1024 1 ; uniform damping
; Initial displacement - (displacement, vel, and acceleration
; Acceleration is from stiffness matrix pos effect - increases acceleration
f6 0 1024 -7 .01 1024 .01 ; uniform initial velocity-displacement
f7 0 1024 -5 .001 1024 1024     ; Trajectory

i1      0.0     6.5     -6      7.00
i1      6.5     6.5     -9      7.07    ; 2 notes
i1      6.5     6.5     -9      7.04
e
</CsScore>
</CsoundSynthesizer>

Yet another example of the scanu2 opcode. It uses the file scanu2-3.csd.

Third example of the scanu2 opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac  --limiter=0.95 ;;;realtime audio out & and limit loud sounds
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o scanu2-3.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

; by Richard Boulanger 2024

instr scan      ; show the pluck options

a0 init 0
irate = .04

kmass line 2,p3,1
kstiff line 10,p3,10
kcenter line 5,p3,6
kdamp line 1,p3,2
kpos line .4,p3,.5

;scanu2 init,irate,ifndisplace,ifnmass,ifnmatrix,ifncentr,ifndamp,kmass,kmtrxstiff,
; kcentr, kdamp, ileft, iright, kpos, kdisplace, ain, idisp, id
scanu2 p6, irate, 6, 2, 3, 4, 5, kmass, kstiff, kcenter, kdamp, p7, p8, kpos, .02, a0, 1, 2
a1 scans ampdbfs(p4), cpspch(p5), 7, 2
a1 dcblock2 a1
outs a1, a1
endin

</CsInstruments>
<CsScore>
f1 0 16 10 1 ; Sine Hammer
f11 0 16 10 1 .5 .3 .2 .1 .01 ; Sawlike hammer
f111 0 16 10 1 0 .73 0 .53 0 .45 0 .17 0 .02 0 .002 ; Pulselike hammer
f2 0 16 -7 8 16 8 ; Masses
f3 0 0 -44 "string_with_extras-16.matrxT" ; Spring matrix, to be found in the examples folder of the manual
f4 0 16 -7 .07 16 .07 ; Centering force, uniform initial centering
f5 0 16 -7 .04 16 .04 ; Damping, uniform damping
f6 0 16 -7 .01 16 .01 ; uniform initial velocity-displacement
f7 0 16 -5 15 16 1 ; Trajectory


i"scan" 0 3 6 7.00 -1 .5 .5 ; pluck in middle
s
i"scan" 0 3 2 7.00 -1 .1 .1 ; pluck at left
s
i"scan" 0 3 0 7.00 -1 .2 -.8 ; 2 plucks up left and down right
s
i"scan" 0 3 -6 7.00 1 .2 .8 ; sine hammer - ignore pluck position
s
i"scan" 0 3 -6 7.00 11 .8 .2 ; sawlike hammer - ignore pluck position
s
i"scan" 0 3 -6 7.00 111 .1 .6 ; pulselike hammer - ignore pluck position
e
</CsScore>
</CsoundSynthesizer>

See also

Scanned Synthesis

More information on the Scanned Synthesis opcodes: Working with Scanned Synthesis, written by Steven Yi, and some tutorials by Richard Boulanger.

Credits

Author: John ffitch
May 2021

New in Csound version 6.16