Main Group 03: Additive Synthesis, Different Units


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Noise/Inharmonics/Fundamental Noise/Inharmonics 1/Inharmonics 2 LFOs Modulate Frequency in Parallel
01
1 drum and snare drum
2A more economic version of 1
2B RAND instead of RANDI
05
1 percussive drum-like
40
1 siren-like glissandi

Overview

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

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


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]

Orchestra and Score

WAV and mp3


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]

Orchestra and Score

WAV and mp3


03_01_2B

additional parameters: none

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

[flowchart]

Orchestra and Score

WAV and mp3


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 The sinus wave has been replaced by a second inharmonic spectrum.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]

Orchestra and Score

WAV and mp3


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]

Orchestra and Score

WAV and mp3


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