View source for Subtractive synthesis

{{short description|Method of sound synthesis}}
'''Subtractive synthesis''' is a method of [[sound synthesis]] in which [[Harmonic_series_(music)#Partial.2C_harmonic.2C_fundamental.2C_inharmonicity.2C_and_overtone|overtones]] of an audio signal are attenuated by a [[audio filter|filter]] to alter the [[timbre]] of the sound. 

==Overview==
Subtractive synthesis relies on source sounds that have overtones, such as [[Sine wave|non-sinusoidal waveforms]] like [[Square wave|square]] and [[triangle wave|triangle waves]], or [[white noise|white]] and [[pink noise]]. These overtones are then [[Modulation|modulated]] to alter the source sound. This modulation can happen in a wide variety of ways, such as [[Voltage-controlled filter|voltage-controlled]] or [[low-pass filter|low-pass filters]].<ref name="JMR"/>

The technology developed in experimental electronic studios which were primarily focused on [[telecommunications]] and military applications.<ref>Iverson, Jennifer. “Fraught Adjacencies: The Politics of German Electronic Music.” ''Acta Musicologica'', vol. 92, no. 1, 2020. 94f.</ref> Early examples include [[Bell Labs]]' [[Voder]] (1937–8).<ref>Dudley, Homer, Richard R. Riesz, and Stanley S. A. Watkins. “A Synthetic Speaker.” ''Journal of the Franklin Institute'' 227, no. 6 (1939): 739–64.</ref> Composers began applying the concept of subtractive synthesis beyond the recording studio in concert music. [[Henri Pousseur]]'s ''[[Scambi]]'' (1957) subjects white noise to filters and uses the resulting sounds to create montages. ''[[Mikrophonie_(Stockhausen)#Mikrophonie_I|Mikrophonie I]]'' (1964) by [[Karlheinz Stockhausen]] uses a tam-tam and a microphone as the primary sound source which is then filtered extensively by two sound projectionists.<ref>Manning, Peter. ''Electronic and Computer Music'', Oxford University Press, Incorporated, 2004. 70, 158.</ref>

Until the advent of [[digital synthesizer]]s, subtractive synthesis was the nearly universal electronic method of sound production.<ref>Bates, Jon. "The History of the World: Part One, Subtractive Synthesis". ''[[Amiga Format]]'', no. 4, 1989 Nov 01, 1989/11/01/, pp. 98.</ref> Its popularity was due largely to its relative simplicity.<ref>Lane, John, et al. “Modeling Analog Synthesis with DSPs.” ''Computer Music Journal'', vol. 21, no. 4, 1997. 23.</ref> Subtractive synthesis was so prevalent in [[Analog synthesizer|analog synthesizers]] that it is sometimes called "analog synthesis".<ref name=KC>{{cite book|last1=Collins|first1=Karen|title=Game Sound: An Introduction to the History, Theory, and Practice of Video Game Music and Sound Design|publisher=MIT Press|isbn=9780262033787|page=10|url=https://books.google.com/books?id=gnw0Zb4St-wC&pg=PA10|language=en}}</ref> It was the method of sound production in instruments like the [[Trautonium]] (1930), [[Novachord]] (1939), [[Buchla_Electronic_Musical_Instruments#Buchla_100_series_(1960s)|Buchla 100]] (1960s), [[EMS VCS 3]] (1969), [[Minimoog]] (1970), [[ARP 2600]] (1971), [[Oberheim OB-1]] (1978), and [[Korg MS-20 ]](1978).<ref name=JMR>Réveillac, Jean-Michel. ''Synthesizers and Subtractive Synthesis 1''. [[Wiley (publisher)|John Wiley & Sons]], 2024.</ref>{{rp|71–4}} [[Programmable sound generator]]s (PSG) relied heavily on subtractive synthesis. PSGs were used in many personal computers, arcade games, and home consoles such as the [[Atari ST]], [[Mattel]]'s [[Intellivision]], [[Sega]]'s[[Master System]], and the [[ZX Spectrum]].<ref name=KC/>

==Nomenclature==
Subtractive synthesis has become a catchall for a method where source sounds are modulated, and it is sometimes applied inappropriately.<ref>de Poli, Giovanni. “A Tutorial on Digital Sound Synthesis Techniques.” ''[[Computer Music Journal]]'', vol. 7, no. 4, 1983. 14.</ref><ref>Stefanakis, Nikolaos, et al. “Sound Synthesis Based on Ordinary Differential Equations.” ''Computer Music Journal'', vol. 39, no. 3, 2015. 48.</ref>

==Method==
The following is an example of subtractive synthesis as it might occur in an electronic instrument to emulate the sound of a [[Pizzicato|plucked string]]. It was created with a [[personal computer]] program designed to emulate an analogue subtractive synthesizer.

===Source Sound===
First, an [[electronic oscillator]] produces a relatively complex [[waveform]] with audible [[overtone|overtones]]. Only one oscillator is necessary, and the number can vary widely. In this case, two oscillators are used:
{|
|- 
| {{Listen | filename = subsynth-wave1.ogg | title = Waveform #1 | format = [[Ogg]] | pos = right | help = yes }}
||
[[File:Waveform 1.jpg|alt=Closeup view of waveform in the audio sample.|thumb|Closeup [[oscilloscope]] of Waveform #1.]]
|-
| {{Listen | filename = subsynth-wave2.ogg | title = Waveform #2 | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Closeup oscilloscope of Waveform 2.jpg|alt=Closeup oscilloscope of Waveform #2.|thumb|Closeup oscilloscope of Waveform #2.]]
|}
[[Pulse-width modulation]] is applied to both waveforms to create a more complex tone with [[vibrato]]:
{|
|- 
| {{Listen | filename = subsynth-wave1pwm.ogg | title = PWM waveform #1 | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Closeup of pulse-width modulated Waveform 1.jpg|alt=Closeup of pulse-width modulated Waveform 1.|thumb|Closeup of pulse-width modulated Waveform 1.]]
|-
| {{Listen | filename = subsynth-wave2pwm.ogg | title = PWM waveform #2 | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Closeup of pulse-width modulated Waveform 2.jpg|alt=Closeup of pulse-width modulated Waveform 2.|thumb|Closeup of pulse-width modulated Waveform 2.]]
|}

The pulse-width modulated sounds are now combined at equal volume. Combining them at different volumes would create different timbres. The result is a 2-second '''source sound''', which is ready for subtractive synthesis.
{| 
|-
| {{Listen | filename = subsynth-wavemix.ogg | title = Combined waveforms | format = [[Ogg]]}} 
|| 
[[File:Combined waveforms and pulse-width modulation.jpg|alt=Combined waveforms and pulse-width modulation.|thumb|Combined waveforms and pulse-width modulation.]]
|}

===Subtractive Synthesis===
The combined wave is passed through a [[voltage-controlled amplifier]] connected to an [[Envelope_(music)#ADSR|envelope generator]]. The parameters of the sound's envelope (attack, decay, sustain and release) are manipulated to change its sound. In this case, the decay is vastly increased, sustain is reduced, and the release shortened. The resulting sound is audible for half as long as the source sound:
{|
|- 
| {{Listen | filename = subsynth-mixenv.ogg | title = Enveloped sound | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Enveloped waveform.jpg|alt=Enveloped waveform.|thumb|Enveloped waveform.]]
|}

With its new envelope, the sound is run through a [[low-pass filter]], which reduces the volume of higher overtones:
{|
|- 
| {{Listen | filename = subsynth-nomodfilter.ogg | title = Low-passed sound | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Low-pass filtered waveform.jpg|alt=Low-pass filtered waveform.|thumb|Closeup of low-pass filtered waveform.]]
|}

To better emulate the sound of a plucked string, the filter's [[cutoff frequency]] is lowered.
{|
|- 
| {{Listen | filename = subsynth-modfilter.ogg | title = Final sound | format = [[Ogg]] | pos = right | help = no }}
||
[[File:Final waveform.jpg|alt=Final waveform|thumb|Closeup of final waveform]]
|-
| {{Listen | filename = subsynth-arpeggios.ogg | title = Some arpeggios | format = [[Ogg]] | pos = right | help = no }}
|}

== See also ==
* {{annotated link|Additive synthesis}}
* {{annotated link|Minimoog}}
* {{annotated link|MicroKorg}}
* {{annotated link|Modular synthesizer}}
* {{annotated link|Korg MS-20}}
* {{annotated link|Novachord}}
* {{annotated link|Steiner-Parker Synthacon}}
* {{annotated link|OSC OSCar}}

==References==
{{reflist}}

==External links==
*[http://alsamodular.sourceforge.net AMS] – A free software synthesis program for [[ALSA (Linux)|ALSA]].

{{Sound synthesis types}}

[[Category:Sound synthesis types]]

[[ru:Субтрактивный синтез]]