modmatrix — Modulation matrix opcode with optimizations for sparse matrices.
The opcode can be used to let a large number of k-rate modulator variables modulate a large number of k-rate parameter variables, with arbitrary scaling of each modulator-to-parameter connection. Csound ftables are used to hold both the input (parameter) variables, the modulator variables, and the scaling coefficients. Output variables are written to another Csound ftable.
iresfn -- ftable number for the parameter output variables
isrcmodfn -- ftable number for the modulation source variables
isrcparmfn -- ftable number for the parameter input variables
imodscale -- scaling/routing coefficient matrix. This is also a csound ftable, used as a matrix of inum_mod rows and inum_parm columns.
inum_mod -- number of modulation variables
inum_parm -- number of parmeter (input and output) variables.
The arguments inum_mod and inum_parm do not have to be set to power-of-two values.
kupdate -- flag to update the scaling coefficients. When the flag is set to a nonzero value, the scaling coefficients are read directly from the imodscale ftable. When the flag is set to zero, the scaling coefficients are scanned, and an optimized scaling matrix stored internally in the opcode.
For each modulator in isrcmodfn, scale it with the coefficient (in imodscale) determining to what degree it should influence each parameter. Then sum all modulators for each parameter and add the resulting modulator value to the input parameter value read from iscparmfn. Finally, write the output parameter values to table iresfn.
The following tables give insight into the processing performed by the modmatrix opcode, for a simplified example using 3 parameter and 2 modulators. Let’s call the parameters "cps1", "cps2", and "cutoff", and the modulators "lfo1" and "lfo2".
The input variables may at a given point in time have these values:
... while the modulator variables have these values:
The scaling/routing coefficients used:
... and the resulting output values:
The output value for "cps1" is calculated as 400+(0.5*40)+(-0.2*-50), similarly for "cps2" 800+(0.5*0)+(-0.2*100), and for cutoff: 3+(0.5*-2)+(-0.2*3)
The imodscale ftable may be specified in the score like this:
f1 0 8 -2 200 0 2 50 300 -1.5
Or more conveniently using ftgen in the orchestra:
gimodscale ftgen 0, 0, 8, -2, 200, 0, 2, 50, 300, -1.5
Obviously, the parameter and modulator variables need not be static values, and similarly, the scaling routing coefficient table may be continuously rewritten using opcodes like tablew
Here is an example of the modmatrix opcode. Play modmatrix.csd
Example 627. Example of the modmatrix opcode.
See the sections Real-time Audio and Command Line Flags for more information on using command line flags.
<CsoundSynthesizer> <CsOptions> ; Select audio flags here according to platform ; Audio out Audio in ;-odac -iadc ;;;RT audio I/O ; For Non-realtime ouput leave only the line below: -o modmatrix.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> sr = 44100 kr = 441 ksmps = 100 nchnls = 2 0dbfs = 1 ; basic waveforms giSine ftgen 0, 0, 65537, 10, 1 ; sine wave giSaw ftgen 0, 0, 4097, 7, 1, 4096, -1 ; saw (linear) giSoftSaw ftgen 0, 0, 65537, 30, giSaw, 1, 10 ; soft saw (only 10 first harmonics) ; modmatrix tables giMaxNumParam = 128 giMaxNumMod = 32 giParam_In ftgen 0, 0, giMaxNumParam, 2, 0 ; input parameters table ; output parameters table (parameter values with added modulators) giParam_Out ftgen 0, 0, giMaxNumParam, 2, 0 giModulators ftgen 0, 0, giMaxNumMod, 2, 0 ; modulators table ; modulation scaling and routing (mod matrix) table, start with empty table giModScale ftgen 0, 0, giMaxNumParam*giMaxNumMod, -2, 0 ;******************************************** ; generate the modulator signals ;******************************************** instr 1 ; LFO1, 1.5 Hz, normalized range (0.0 to 1.0) kLFO1 oscil 0.5, 1.5, giSine ; generate LFO signal kLFO1 = kLFO1+0.5 ; offset ; LFO2, 0.4 Hz, normalized range (0.0 to 1.0) kLFO2 oscil 0.5, 0.4, giSine ; generate LFO signal kLFO2 = kLFO2+0.5 ; offset ; write modulators to table tablew kLFO1, 0, giModulators tablew kLFO2, 1, giModulators endin ;******************************************** ; set parameter values ;******************************************** instr 2 ; Here we can set the parameter values icps1 = p4 icps2 = p5 icutoff = p6 ; write parameters to table tableiw icps1, 0, giParam_In tableiw icps2, 1, giParam_In tableiw icutoff, 2, giParam_In endin ;******************************************** ; mod matrix edit ;******************************************** instr 3 ; Here we can write to the modmatrix table by using tablew or tableiw iLfo1ToCps1 = p4 iLfo1ToCps2 = p5 iLfo1ToCutoff = p6 iLfo2ToCps1 = p7 iLfo2ToCps2 = p8 iLfo2ToCutoff = p9 tableiw iLfo1ToCps1, 0, giModScale tableiw iLfo1ToCps2, 1, giModScale tableiw iLfo1ToCutoff, 2, giModScale tableiw iLfo2ToCps1, 3, giModScale tableiw iLfo2ToCps2, 4, giModScale tableiw iLfo2ToCutoff, 5, giModScale ; and set the update flag for modulator matrix ; ***(must update to enable changes) ktrig init 1 chnset ktrig, "modulatorUpdateFlag" ktrig = 0 endin ;******************************************** ; mod matrix ;******************************************** instr 4 ; get the update flag kupdate chnget "modulatorUpdateFlag" ; run the mod matrix inum_mod = 2 inum_parm = 3 modmatrix giParam_Out, giModulators, giParam_In, \ giModScale, inum_mod, inum_parm, kupdate ; and reset the update flag chnset 0, "modulatorUpdateFlag" ; reset the update flag endin ;******************************************** ; audio generator to test values ;******************************************** instr 5 ; basic parameters iamp = ampdbfs(-5) ; read modulated parameters from table kcps1 table 0, giParam_Out kcps2 table 1, giParam_Out kcutoff table 2, giParam_Out ; set filter parameters kCF_freq1 = kcps1*kcutoff kCF_freq2 = kcps2*kcutoff kReso = 0.7 kDist = 0.3 ; oscillators and filters a1 oscili iamp, kcps1, giSoftSaw a1 lpf18 a1, kCF_freq1, kReso, kDist a2 oscili iamp, kcps2, giSoftSaw a2 lpf18 a2, kCF_freq2, kReso, kDist outs a1, a2 endin </CsInstruments> <CsScore> ;******************************************** ; set initial parameters ; cps1 cps2 cutoff i2 0 1 400 800 3 ;******************************************** ; set modmatrix values ; lfo1ToCps1 lfo1ToCps2 lfo1ToCut lfo2ToCps1 lfo2ToCps2 lfo2ToCut i3 0 1 40 0 -2 -50 100 3 ;******************************************** ; start "always on" instruments #define SCORELEN # 20 # ; set length of score i1 0 $SCORELEN ; start modulators i4 0 $SCORELEN ; start mod matrix i5 0 $SCORELEN ; start audio oscillator e </CsScore> </CsoundSynthesizer>