Unison after FM

Double checking: it’s currently not possible to apply unison to a FM waveform, right?
(without resynthesizing the preset)

Should not be a problem if you use one oscillator to modulate another. You apply unison to the carrier (modulated oscillator).
However, if you use an LFO to fm an oscillator, the results is going to be very bad.

Thanks for your reply. I didn’t manage to get it right yet, so I will try to elaborate the question.


This is a basic FM waveform. It sounds like this:


When I apply unison to the carrier (8 randomized voices, 20%), it introduces a weird phasing effect.
(Please correct me if i did the wrong way)


If I resynthesize the base preset it to a single oscilator instead, and then apply unison. I get the sound I’m looking for. This is also how unison sounds in FM-8 or Massive.

Is it possible to achieve this without resynthesizing?

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yes same here if i try this.

maybe @Tytel wants to take a look at this.

Is it really a bug? I would kind of expect the oscillator modulations to happen after unison, based on the way the UI is laid out. But I wouldn’t mind the option to have unison after the modulations.

That’s weird. I will try this later on as well.

FM is done per unison voice before adding them together so e.g. the unison voices that are tuned down will sound different than the voices that are tuned up and then are combined.

The order you’re looking for doesn’t really make sense with ‘live’ FM. Preprocessing an FM table is the way to go for what you want (looks like you already did that)

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Is it?
I didn’t really have that impression, I made many patch doing precisely that and they sound quite right in my book, at least doing phase modulation as with the FM algoritm

@thijs why are you surprised by the phasing effect? Wouldn’t you expect it out of unison anyway?

In fact, I checked other synths with a similar FM routing (FM: OSC2 > OCS1) and unison sounded right. In Vital it just doesn’t sound right. It is pulsating and weird. It there any reason for this?

You’ll need to upload some examples if you’re going to compare to other synth’s sounds

Hi Matt, I have attached the audio file. They both have very similar unison settings.https://vitalpublic.s3.dualstack.us-west-2.amazonaws.com/original/2X/5/583752c071f2a608594b3671bf080cf7908c31a0.mp3

So the example from thijs is valid. How to overcome this? Because otherwise, a nice unison with FM sounds is not possible right now.

Can you try it while turning down the phase randomization amount from 100% to 0%?

The audio sample had a phase randomization set to zero on the modulator and 100 on the carrier. I will try to set both to zero and come back.

It’s not about phase randomization - Matt’s actually explained it pretty clearly: in Vital, the unison is applied first, then the frequency modulation. So you’re modulating a number of very slightly different pitches with the one pitch that isn’t always in a prefect integer ratio to them. As I understand it, that’s what creates the phasey effect. In other synths, like Massive, the unison is applied after the frequency modulation, which you can achieve in Vital by doing exactly what the OP did, ie re-synthesizing the frequency modulated oscillator and using it as a base wave.
Obviously, the disadvantage of this is that you can’t modulate the FM amount. I hesitate to suggest it (I feel like there are already way too many “improvement” suggestions out there for what is already an amazingly innovative new synthesizer) but perhaps an option to have unison applied after FM could be a feature implemented in the future?

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