TOOT 6

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The first character in a score statement is an opcode, determining an action request; the remaining data consists of numeric parameter fields (p-fields) to be used by that action. So far we have been dealing with two different opcodes in our score: f and i. i statements, or note statements, invoke the p1 instrument at time p2 and turn it off after p3 seconds; all remaining p-fields are passed to the instrument.

On the other hand, f statements, or lines with an opcode of f, invoke function-drawing subroutines called GENS. In Csound there are currently twenty-three GEN routines which fill wavetables in a variety of ways. For example, GEN01 transfers data from a soundfile; GEN07 allows you to construct functions from segments of straight lines; and GEN10, which we've been using in our scores so far, generates composite waveforms made up of a weighted sum of simple sinusoids. We have named the function "f1," invoked it at time 0, defined it to contain 512 points, and instructed GEN10 to fill that wavetable with a single sinusoid whose amplitude is 1. GEN10 can in fact be used to approximate a variety of other waveforms, as illustrated by the following:

f1 0 2048 10 1                                         ; Sine
f2 0 2048 10 1 0.5 0.3 0.25 0.2 0.167 0.14 0.125 .111  ; Sawtooth
f3 0 2048 10 1 0   0.3 0    0.2 0     0.14 0     .111  ; Square
f4 0 2048 10 1 1   1   1    0.7 0.5   0.3  0.1         ; Pulse

For the opcode f, the first four p-fields are interpreted as follows:

p1 - table number - In the orchestra, you reference this table by its number.

p2 - creation time - The time at which the function is generated.

p3 - table size - Number of points in table - must be a power of 2, or that plus 1.

p4 - generating subroutine - Which of the 17 GENS will you employ.

p5 - meaning determined by the particular GEN subroutine.

 In the instrument and score below, we have added three additional functions to the score, and modified the orchestra so that the instrument can call them via p11.

orchestra

 File: Toot06.orc
instr 6

ifunc     =         p11                                ; select the basic waveform

irel      =         0.01                               ; set vibrato release time

idel1     =         p3 * p10                           ; calculate initial delay (% of dur)

isus      =         p3 - (idel1 + irel)                ; calculate remaining duration



iamp      =         ampdb(p4)

iscale    =         iamp * .333                        ; p4=amp

inote     =         cpspch(p5)                         ; p5=freq



k3        linseg    0, idel1, p9, isus, p9, irel, 0    ; p6=attack time

k2        oscil     k3, p8, 1                          ; p7=release time

k1        linen     iscale, p6, p3, p7                 ; p8=vib rate



a3        oscil     k1, inote*.999+k2, ifunc           ; p9=vib depth

a2        oscil     k1, inote*1.001+k2, ifunc          ; p10=vib delay (0-1)

a1        oscil     k1, inote+k2, ifunc



          out       a1+a2+a3

          endin

score

 File: Toot06.sco
f1   0    2048 10   1                                                                ; Sine

f2   0    2048 10   1    0.5  0.3  0.25 0.2  0.167     0.14      0.125     .111      ; Sawtooth

f3   0    2048 10   1    0    0.3  0    0.2  0         0.14      0         .111      ; Square

f4   0    2048 10   1    1    1    1    0.7  0.5       0.3       0.1                 ; Pulse



;ins strt dur  amp       frq       atk       rel       vbrt vbdpt     vibdl     waveform

i6   0     2   86        8.00      .03       .7        6    9         .8        1

i6   3     2   86        8.02      .03       .7        6    9         .8        2

i6   6     2   86        8.04      .03       .7        6    9         .8        3

i6   9     3   86        8.05      .03       .7        6    9         .8    
 

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