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Main Group 03: Additive Synthesis, Different Units
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Sub Id  Contents

01      Noise/Inharmonics/Fundamental
    1   drum and snare drum
    2A  more economic version of 1
    2B  RAND instead of RANDI

05      Noise/Inharmonics 1/Inharmonics 2
    1   percussive drum-like

40      LFOs Modulate Frequency in Parallel 
    1   siren-like glissandi

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Overview

This main group contains additive instruments composed of
different building blocks.

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Suggested Reading

Moore, F.R. 1990.
"Additive Synthesis."
in Elements of Computer Music.
Prentice-Hall, pp. 207-227.

Risset, J.-C. 1969.
"Introductory Catalogue of Computer Synthesized Sounds."
Murray Hill, N.J.: Bell Telephone Laboratories

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03_01_1
additional parameters: iamp2, iamp4, ifq5, ifq7


This instrument forms the sum of a noise band, sine wave and an
inharmonic spectrum. 

Noise band.
Parameter ifq5 tells us the center frequency of the noise band,
ifq7 gives half of its bandwidth and its envelope is controlled
by the exponential f52 (1-2-12).

Fundamental.
The wave of function 12 plays the 10th harmonic of the
fundamental frequency ifq1. Setting ifq1 to 20Hz will produce a
sinus at 200 Hz. 

Inharmonic spectrum.
The parameter ifq1 is used again to build an inharmonic spectrum
from a wave that contains only high frequency components
(harmonics 10,16,22 & 23).

Section 1 plays a snare-like tone, with a noise centered at 4000
Hz and a bandwidth of 3000 Hz. 

Section 2 turns the snares off (iamp7 = 0) and plays four
pitches: 120, 140, 150 and 160 Hz.

In section 3 the snares return with a rhythmic pattern.
(Risset 1969: #400)

(flowchart)
(.orc and .sco files)

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03_01_2A
additional parameters: none


This is a more efficient implementation of 03_01_1: some constant
parameters have been moved into the orchestra, and the amplitude
of the three building blocks is expressed as function of the main
iamp variable. (Vercoe 1993: morefiles/risset2.orc; Vercoe 1993:
morefiles/drum.orc)

(flowchart)
(.orc and .sco files)

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03_01_2B
additional parameters: none


A version with RAND instead of RANDI sounds very 
different! The noise quality is brighter.

(flowchart)
(.orc and .sco files)

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03_05_1
additional parameters: if1, if2


In this realization of the drum instrument, the amplitudes of the
three building blocks are fixed at the same level. The sinus wave
has been replaced by a second inharmonic spectrum. The wave
tables for the inharmonic fields are now controlled from the
score file. F14 and f15 include very high harmonics from 25 to
100, resulting in a more metallic tone for the second group of
three notes. (Risset 1969: #410 sec 1 & 2)

(flowchart)
(.orc and .sco files)

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03_40_1
additional parameters: amplitudes, rates and frequencies          
                       of four different building blocks


We have here four different building blocks to create this
chaotic sinus field. In all cases an LFO function controls the
pitch evolution; the scanning rate varies with irate.

The unit at the left should have a feedback added to correspond
to the original. The second unit produces a variable pitched
noise band and the third a variable pitched inharmonic field
(f12). The last module gives a sinus glissando contour. (Risset
1969: #510)

(flowchart)
(.orc and .sco files)
