Buchla Style Complex Oscillator

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E8_Heterotic
Posts: 30
Joined: Wed Dec 19, 2018 4:05 am

Buchla Style Complex Oscillator

Post by E8_Heterotic » Wed Jan 02, 2019 4:00 am

This is just a little thing I put together, but it's reasonably powerful. It's based on the Buchla style of synthesis. It's called a complex oscillator, which involves a master oscillator (the output), a modulating (for FM on the master) oscillator, and a wave shaper for the output of the master oscillator. The FM together with wave shaping gives a large amount of control over the output waveform.

Controls:

1. Modulator Waveform (It's an Analog Generator module)
2. Modulator Duty Cycle
3. Modulator Attack
4. Modulator Release
5. Modulator Sustain
6. Master Waveform (It's a basic Generator module)
7. Master Duty Cycle
8. Master Attack
9. Master Release
10. Master Sustain
11. Modulation Depth (This controls the "FM by input" controller on the Generator module.)
12. Modulator Frequency (This controls the "Transpose" setting on a MultiSynth module attached to the Modulator oscillator.)
13. Modulator Finetune (Ditto but for the Fine Tuning of the MultiSynth.)
14. Master Frequency
15. Master Finetune
16. WaveShaper Symmetry Mode (This controls whether or not the WaveShaper module is in symmetric mode or not.)

Unfortunately, you can only control the wave shaping envelope by going into edit mode on the module. The same is true if you choose a drawn waveform on either the Master or Modulator oscillators. To actually draw the waveform or to draw the wave shaping envelope, you must open up the edit mode on the module.

However, thanks to the large number of controllers, you can put (full ADSR) envelopes and/or LFO outputs on everything. If you want an ADSR on the Modulator, I recommend turning the Modulator's attack and release to 0, it's sustain on, and putting an envelope on the Modulation Depth controller.
complex oscillator.sunsynth
Buchla Oscillator
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E8_Heterotic
Posts: 30
Joined: Wed Dec 19, 2018 4:05 am

Re: Buchla Style Complex Oscillator

Post by E8_Heterotic » Sat Jan 05, 2019 3:45 pm

I added some functionality to the oscillator. Now it can do AM and PM as well. I have a modulator module which handles the AM or PM (or Abs PM). This is hooked up to the waveshaper. The output of the master oscillator is hooked up to an amp which goes into the waveshaper. The signal received by the waveshaper is the sum of the generator's (possibly FM) signal and the modulator's AM/PM signal. The amp and the modulator both have volume controls, so you can always shut either of them off. In addition, there is an amp going from the modulating oscillator into the modulator module so you can control the "depth" of the AM/PM. The module now has 21 custom controls and is highly customizable. You still need to open it in edit mode to draw the waveshaper envelope and the drawn waveforms of the oscillators, but unfortunately, I can't do anything about that.

The PM choice may seem redundant, but it's actually not. PM differs from FM in several ways:

1. Technically, PM is FM but with the derivative (rate of change) of the modulating oscillator being used instead of the modulator being used directly. Even with sine waves, this means that PM sounds different at different frequencies since higher frequency signals have larger derivatives. So, to get the same effect as FM, you have to lower the modulation depth as a function of frequency in order to compensate for this.

2. With any signal other than sine waves, PM and FM are quite different. PM with a triangle wave sounds like FM with a square wave. PM with a square or sawtooth wave basically does nothing except some weird popping noises due to Gibbs overshoot. PM with any other waveforms will also sound different from FM. Sine waves are special because they are (essentially) proportional to their own derivatives.

3. Even with the sine wave, you have to shift the signal's phase to get the exact same effect as FM even at a fixed frequency. This is because the derivative of a sine/cosine wave phase shifts the wave by 90 degrees.

4. In general, PM seems to sound "harsher" than FM. This is likely due to the fact that integration tends to smooth out functions, so derivatives tend to make functions "bumpier."
complex oscillator.sunsynth
Buchla Oscillator
(13.54 KiB) Downloaded 194 times

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