What is it that creates the wavy effect when to oscillators go into a mixer like so:
The waves are slower at lower pitch and faster in higher pitch, is it the phase of the oscillators which become apparent when there is 2 of them?
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is there a way to control how it beats?
Or that is, maybe to understand what to control that makes it beat differently.
I would love to have irregular beating if possible
The beating is determined by the coincident phases of close but not identical frequencies, usually controlled by changing the frequency of at least one of the signals. This is how one tunes a stringed instrument: sounding the same note on two strings and adjusting string tension (frequency) until the beating goes away.
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I think I have misunderstood - your oscillators are the same frequency, but out of phase. That’s another effect. You can try to introduce a short delay on one oscillator, to control it’s phase, relative to the other / or use another (dual) VCO with controllable phase relation.
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the oscillators are slightly detuned, or different pitch entirely.
Beat rate = the diff in Hz. If one plays 440 Hz and the other 441, the beating will happen at 1Hz.
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I would love to have irregular beating if possible
Add an LFO with a very small amplitude (like bogaudio llfo with scale set to 2-3%) to modulate either the pitch cv of the oscillator, or to modulate the phase of the output waveform (like bogaudio cvd set to 100% wet and lfo into the time cv input).
And if that is not irregular enough, add another instance of the lfo to modulate the v/oct input on the first lfo!
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The SurgeXT oscillators can do this, since they have both detune and drift (drift is in the context menu).
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I recommend using sine waves to hear the cleanest beating.
Every harmonic of more complex waves will contribute its own beating that will be different than the others. I think it is also easier for our brains to detect the pitch variation when there are harmonics involved. With pure sine waves we are more likely to hear the beating without detecting the pitch variation.
Another option for irregular beating is to use three oscillators, one out of tune negatively, and another out of tune positively by a different amount. Instead of modulating frequency, use VCAs to modulate the volume of the detuned oscillators from off to full at different rates with a pair of LFOs. I just tried it out, and it sounds pretty cool.
Irregular Beating.vcv (2.2 KB)
I suppose at this point you could argue why don’t I simply modulate the volume of a single oscillator. 
In a related technique, you can use the beating effect to create stereo panning with two detuned oscillators droning at constant volume. One oscillator goes to both left and right channels. The detuned oscillator goes to the left channel, and an inverted copy goes to the right. The inversion causes the left and right channels to be 180 degrees out of phase. So the left and right alternate as to which has constructive interference and which has destructive interference.
Detuned panning.vcv (2.1 KB)
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One other important concept. For a given amount of detuning, the beat frequency increases as the pitch increases. There is a mathematical formula that lets you detune to a constant beat frequency rate. I don’t remember what it is, but I used it in my Venom Harmonic Quantizer (HQ) module.
Harmonics are often used when doing linear FM or amplitude modulation or ring modulation etc. If you detune the harmonic, then you also get a beat frequency.
There is a detune amount (AMT) knob, as well as a compensation (COMP) knob. With the compensation at 100%, the beat frequency will remain constant as the pitch changes. At 0% there is no compensation.
You can use HQ for consistent simple detune beating by keeping the harmonic at 1, as I have done in the following patch.
Consistent detune beat rate.vcv (2.2 KB)
I am using 2 channel polyphony where the second VCO channel is detuned from the first.
The HQ Detune AMT knob sets the amount of detune. The COMPensation is at 100%. Adjust the pitch with the top KNOB 5 knob and the beat frequency should not change. Play around with different compensation levels and see what happens.
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Not to swerve the topic, but every time I pull down the context menu with Surge oscillators to adjust the output level, I think – oh dang, I was meaning to play with the Drift function here. And then I do the same thing a week later.
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It sound like a spaceship 
Or heave machinery
Thank you for all the patches. Is the beating the same thing that happens when a filter has an oscillator going thru it and the filter is modulated with an LFO?
I am not familiar with that.
If the resonance is high it might be due to the cutoff sweeping through individual harmonics within the input signal. Each time it hits a specific harmonic there could be a volume jump.
I think what i am trying to say is simply when you FM an oscillator with a filter.
I think you meant to say use an LFO (or VCO) to FM the filter cutoff. Sure, I am familiar with that. I am just not familiar with beating coming out of that technique.
