Explaining Why Subtractive Synthesizers Don't Have Sine Waves

Tutorial | Mar 07, 2023

In this video, I explain why there is no sine wave in a classical subtractive synthesizer. This is because sine wave has no overtones and therefore makes no sense in terms of subtractive synthesis. I explain how the filter section can be used to target and amplify the fundamental frequency as well as other partials in the harmonic series. I also provide an overview of other synthesis methods such as additive synthesis, Wavetable synthesis, FM synthesis, phase distortion, vector synthesis, granular synthesis, and physical modeling. In each of these methods, sine waves make more sense. Finally, I explain why a saw and pulse waveforms are used in polysynth - because they give different harmonic overtones.

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Questions & Answers #

Maybe you dont watch the video, here are some important takeaways:

What is subjective synthesis? #

Subjective synthesis is a sound synthesis method where complex waveforms are generated by oscillators, mixed together in a specific way, and then shaped with filters to reduce and adjust the overtones. It is used to create sounds with a wide range of timbres and tones.

Why don’t subjective synthesizers have sine waves? #

Subjective synthesizers do not have sine waves because they make no sense in terms of subjective synthesis. Sine waves do not contain any overtones, so it would not be possible to create a sound with a sine wave alone.

How can subjective synthesis be used to target and adjust overtones? #

Subjective synthesis can be used to target and adjust overtones by using a filter to reduce the overtones from a complex waveform and create a sound. Additionally, the resonance can be used to target the fundamental frequency of the sound and make it more pure.

What other synthesis methods are there? #

Other synthesis methods include additive synthesis, which combines a large number of sine waves into a composite sound; FM synthesis, which uses frequency modulation to create complex sounds;

Transcription #

This is what im talking about in this video. The text is transcribed by AI, so it might not be perfect. If you find any mistakes, please let me know.
You can also click on the timestamps to jump to the right part of the video, which should be helpful.

[00:00.000] Hey folks, in today's video, it's about the question why it doesn't have the
[00:04.640] Polysynth no sine wave. And the answer to that is because no subjective
[00:11.960] synthesizer actually has a sine wave because it makes no sense in the terms
[00:18.840] of subjective synthesis method. Subjective synthesis is all about having a rich
[00:26.640] waveform. You start with going into a mixing section where you can combine
[00:31.520] different complex waveforms, and then you use a filter and reduce the
[00:36.560] overtones from this waveform to create a sound. And the sine wave doesn't have
[00:43.080] any overtones, so it makes no sense to have a sine wave inside of a classical
[00:49.520] subjective synthesizer. And when we play here a sound and see we have here all
[00:58.760] these overtones and then you use a filter and we can reduce all these
[01:05.680] overtones in volume to create a sound. And to make a pure sound or much more
[01:13.560] purer sound than this than the song with all these overtones, we can use the
[01:20.120] filter for that of course. So we can double click here the filter to go down
[01:25.920] to C3 and use here the key tracking. So now when we press a key for instance here
[01:32.720] D sharp, D sharp 3, I think that's D sharp 3 here. The filter frequency is
[01:39.000] exactly on the key of D sharp 3, also this frequency. So now when we use here
[01:47.000] the resonance, we can target or increase the fundamental frequency just with the
[01:53.160] resonance. So we get a more pure sound out of this. You have still some overtones
[02:01.600] here but not too much. When we change the frequency on the keys, the filter also
[02:08.520] switches to the right frequency here.
[02:16.160] So okay, we can target basically the fundamental frequency with the filter
[02:21.120] here reset to C3 and using the key track. You can also do something like on bass
[02:27.680] sounds. So let's say you have this bass sound here. Let's take this sound you can
[02:37.720] see it better here. I'll do, can I increase here this?
[02:47.120] So you want to target maybe the second partial here, right? You can do that too.
[02:53.280] So instead of going to C3, C3, you go to C4, which is the next partial in the
[02:59.960] harmonic series and then you increase the resonance. You can see we increase here
[03:08.960] the second partial and it also switches around with the key change. We can use
[03:18.600] that to make this the bass sound or the sub bass more audible on you know laptop
[03:24.560] speakers, headphones and so on. You can also target here the third one, this one,
[03:30.080] by going to, what's that G4? Yeah, G4. So you can basically go up your
[03:45.040] harmonic series and target each of these partials with the resonance here
[03:51.160] differently and just amplify something or even reduce it by using here a notch
[04:02.360] or reduce here the fundamental or the second one. So that's basically how
[04:14.400] subjective synthesis works. You have a complex waveform and then you use the
[04:18.720] filter section to remove all these overtones and create a sound out of it.
[04:24.600] There's also a synthesis method that's exactly the opposite and that's, so we
[04:33.120] have here all the sound synthesis methods. The first one is subjective
[04:36.520] synthesis. Complex waveforms are generated by oscillators, right? And then
[04:42.120] shaped with filters. And then we have your additive synthesis, a large number of
[04:47.320] waveforms, usually sine waves are combined into composite sound, into a
[04:51.880] composite sound. So with this additive synthesis, you basically have an
[04:57.560] oscillator for each of these partials here and you can influence each of these
[05:01.360] partials with these oscillators. And it's probably the most powerful
[05:06.520] synthesis method because you can create any sound imaginable with this method.
[05:11.880] But it's also the most complex to control synthesis method because you
[05:19.320] have to take control of each of these partials here. Maybe there are thousands
[05:24.600] of them and each of them, each of these partials can have a frequency, can have
[05:30.960] a loudness, a different volume, and they can change over time. So when you press a
[05:35.360] key, right, when you have here an envelope, so each of these partials can
[05:39.800] have a different envelope, a different volume envelope. So that's, that's, that
[05:47.760] makes the additive synthesis methods so complex or hard to control. And that's
[05:53.960] why a lot of people just go back to subjective synthesis because it's
[05:58.360] straightforward to start with the complex waveform. You have sometimes here even two
[06:02.440] waveforms you can combine to make the overtones even more complex. And then you
[06:08.200] reduce the overtones here with the filter and you, yeah, get very far with
[06:12.920] this. You can create a lot of sounds with this. Okay, so just to show you some more
[06:19.200] examples, this is the PolyCenture of Bitwig Studio. Let's go here to Monarch,
[06:24.760] which is also a classical, monophonic, subtractive synthesizer. You can see we
[06:31.240] have your oscillator section, three oscillators. You can mix in with the mixing
[06:35.920] section. And at the end we have your filtering section. And that's the
[06:40.360] classical, as most classical as you can go with this, with the subtractive
[06:45.920] synthesizer, oscillator, mixing and filter to reduce overtones, right? Also
[06:53.720] here with the CS80, we have here oscillators, also complex. We have only
[06:58.400] poles here in try and saw. Yes, we have here a sine, but that's an LFO to
[07:05.200] modulate actually here, the pitch. But here also you have two oscillators, one
[07:10.160] oscillator here, one oscillator here. And you have only try and saw. And then
[07:16.080] there's a mixing section, I think here you can mix it. And we have also here
[07:20.840] envelopes for the filter. So yeah, so oscillator, mixing and filter. Again,
[07:28.040] classical setup. Also Diva here by UHE, classical setup. We have
[07:34.480] oscillators, three oscillators. Also here saw, try, saw, poles, poles width and so
[07:41.600] on. Only rich, complex waveforms with a mixing section filter at the end to
[07:48.560] reduce the overtones as you like. So every subjective synthesizer is this way.
[07:54.840] There is no sine wave in there. You maybe have something like, something like
[08:03.360] polymer, which is a Wavetable synthesizer. But here with the wave
[08:12.280] table synthesizer, you can replace the Wavetable with anything you like. So it's
[08:17.400] basically also just a classical subtractive synthesizer because we have
[08:21.840] an oscillator, we have a filter, and we have also here a mixer. Mixer somewhere.
[08:27.520] No, it's not really a mixer, but we have here an oscillator and just a filter
[08:31.680] and envelope, but also classical setup. And you probably also want to have your
[08:37.280] rich, complex waveform in here, which mostly people use, of course, for
[08:43.080] baselines and so on. So it actually makes sense to have a filter here, right?
[08:54.280] To filter something. So this is also something. With other subjective synthesis
[09:08.360] methods, sine waves make more sense. Like I said, an additive synthesis, also FM,
[09:13.840] also phase distortion. There it makes sense because the whole synthesis method
[09:19.080] is about combining sine partials to make complex sound waves out of it, sample
[09:26.560] based vector synthesis, granular. Yeah, it probably doesn't make sense to have a
[09:32.200] sign in there. And physical modeling, maybe there, I don't know. So yeah, I just
[09:39.560] want to give you an explanation why we don't have here a sine oscillator in the
[09:45.560] polysyn because it's a classical subtractive synthesizer. It makes no
[09:49.440] sense to have a pure waveform in there because then the filter have any work to
[09:55.440] do. And that's the explanation. I hope it makes sense. What I can explain
[10:03.520] additionally is why we have here, why we have a sub or why we have a pulse in the
[10:10.440] saw because these two waveforms gives you different overtones. I think the
[10:20.840] saw here gives you basically even harmonics and the pulse gives you even
[10:27.920] an odd harmonics. Okay, so you can start with different
[10:37.760] harmonic setting on the overtones and then act with the filter on it. I put a
[10:43.600] link in the description below where I can read all this stuff on Wikipedia if
[10:46.760] you want to, if you want to go more into detail. But I want to give you a rough
[10:51.120] idea how this works and why we don't have sine partials or sine oscillators in
[10:56.360] classical subtractive synthesis. Thanks for watching. Leave a like if you like the
[11:00.640] video, subscribe to the channel. Thanks for watching and see you in the next video. Bye.