VCO vs Resonators

Hi all.
So I found myself playing with AH’s revamped PRISM Rainbow module this afternoon. Then I asked myself “what’s the difference between a VCO and a resonator?”.

Yes, I know what a VCO is :roll_eyes: But if I would try to explain a resonator to a newer newb than I am then I would freeze up.

So in 25 words or less, what makes a resonator a different noise making module than a VCO and why/how? A brief web search returned not much. Best dressed answer wins a “thumbs up” :grin:


A resonator is built out of a resonating filter, usually, a band pass filter, and usually, more than one resonating at different frequencies. Prism for example has 6.


from Wikipedia:
A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. Musical instruments use acoustic resonators that produce sound waves of specific tones.

and more from thre electronic side of things:

The oscillator is an active circuit which produces periodic voltage or current signals. The resonator is a passive device whose impedance changes rapidly with frequency over a very narrow frequency range.

1 Like

AH! So a resonator is actually a system of VCO+VCF. I had imagined it as some discrete component.

Thank you @Omri_Cohen and @rsmus7 :+1:

1 Like

As an aside, and absolutely no disrespect intended to @johnhoar, but when I first saw Prism I thought “meh”. Why? Because it looked, um, uninteresting to me as a newb. But when it got re-released with the new ‘sexy’ UI, it caught my attention. Now I have spent the last few days playing with it after watching @VCVRackIdeas video and the 4ms version from DivKid.

More rabbit holes :rabbit:

I guess that old advertising adage “Sex sells” is still valid :wink:

Don’t judge a book by its cover!

Surely, don’t judge a module by it’s faceplate :rofl:

Yeah but that’s not the idiom.

The way I think of it is that an oscillator is like a vibrating guitar or violin string (which produces a set of frequencies) and a resonator is like the body of the guitar or violin (which accentuates some frequencies and diminishes others, shaping the sound). The reason a violin sounds different from a guitar when you pluck the string is because of the size, shape, and material of the body (mostly).

But it’s a bit more complicated than that, because in the case of a guitar or violin, the string is also a resonator, which is excited by a burst of white noise (the pluck of the guitar) or a sustained noise (the bow). Strings, pipes, plates, drum-head membranes, and wooden and metal bars have all been modeled mathematically in software and in modules.

Some resonator modules (e.g. Rings) include their own white noise pluck inputs, for convenience, so you could consider them resonators that have the potential to excite themselves. Even so, they’re not oscillators, because they don’t produce a static or varying set of frequencies that is indefinitely sustained.

The important thing to bear in mind with resonators (which are my favorite kind of module - in my view nothing else produces such rich and interesting timbres) is that it makes a big difference what you send into them. If a resonator isn’t doing what you want, feed it something else - a sample, maybe, or a richer or more complex waveform, or a more modulated noise source. In Madrona Labs’ wonderful VST Kaivo I made a beautiful plucked bass sound by using a granulated sample of a squeaky bicycle pump. The squeaks, when they went through the models of the string and instrument body, sounded like a finger sliding along a string to a different fret.

Happy patching!


Yeah, the sad truth is that most of us VCV devs are lucky to have a single talent. It might be great product ideas, it might be DSP programming, it might be UX design. the result is that there are a LOT of amazingly good modules with “meh” panels.

1 Like

Hi christian and thanks. Nice conceptualization there :+1:
PS. Welcome to the community :smile:

True, but often we use them with the resonance cranked so that they make pitches. In that case it’s acting more like the string of a guitar or piano, right?

Squinky thanks for all your hard work and great modules!

Yes. But - please correct me if I’m wrong - to get that you usually have to put in some kind of exciter into the resonator, right? even if the resonator module has it built in?

I would agree that a lot of what is great about resonators is that something that may not be pitched at all goes in, and something that has pitch and harmonics comes out. In which case yes it’s acting exactly like the string of a guitar or violin.

The thing that really helped me understand all this is that when you pluck a guitar string you’re essentially providing a very short burst of white noise. When you bow a violin string, the bow is just rubbing the string - it’s a sustained input of essentially white noise. The resonating string and body are doing all the rest of the magical transformation of the sound. Putting a complex sample in might have very interesting results, and it’s something you can’t really do with a guitar or a violin, but you can do with a hardware or virtual synth.

1 Like

Yes, you are completely correct here. Great description. And thanks for the kind words about the Squinky modules…