Cutoff knob is modulating frequency

[jamespianoo]

Hi there everyone,

I'm making a patch based on F1 P39 "Ice Bowl", but I'm finding that the cutoff, velocity, and key amount knobs are modulating the frequency instead. I've turned off all the LFO's, modulation, and aux envelope and nothing is working. Anyone got any ideas?

It sometimes feels like there's an extra layer to the patches which can't be altered. As you'll try and change a patch by fiddling with loads of knobs and nothing at all happens and then moving a random one will irreversibly change everything. Maybe I'm being a noob here but I've never had any trouble with the Prophet 6 or my Moog for example.

Thanks!

J

[timboréale]

The filter resonance is an oscillator in this patch, so it's normal that the filter envelope controls would be changing the pitch. This is a usual and common trick in synthesis to use the filter resonance as an extra oscillator.

[jamespianoo]

That's good to know thanks. I'm just curious as to how I would edit that though - is it hard wired in or can I manually change that?

[timboréale]

Just turn the resonance down.

[jamespianoo]

Doing that means that there is no pitch and just noise. Is there anyway of adjusting cutoff on this patch like a conventional patch?

[timboréale]

You're asking questions that indicate you may not have studied much about synthesis fundamentals and the architecture of the Rev 2. I think you might be best served by learning more about synthesis fundamentals first!

Understand the oscillator section and how the oscillators produce sound and route it to the filter section with just an init patch: press and hold, simultaneously, the up and down transpose buttons and the hold button - press all three, and then release, the patch will sound very boring and rather horrid. This is a basic patch where you can start to explore the simple functionality of each section without worrying too much about interaction with the others. Go through the manual carefully, trying only one concept at a time, until you have a good grasp on how things functionally work. Then you'll know enough to start taking apart factory patches and understanding how they're put together. Until you have a functional model in your head of how things work, though, you'll just be grasping in the wind when trying to understand somebody's else's patchwork.

[jamespianoo]

Um ok. Thanks for the advice but, for the record I have had this synth for a few years, made plenty of patches, and would say I have a decent understanding of how synthesis works, although I am hardly an expert and can always learn more.

What confused me here is that the routing on this specific patch is completely different to creating a regular patch, and an explanation does not appear to be in the guidebook. Going from an absolute basic patch it is easy to understand how to modulate, LFO and assign parameters but going inside someone else work can be difficult and frustrating - to which I was just wondering if there was a way of making the cutoff a bit more intense as literally every knob and parameter on this patch (from what you said a type of resonance oscilation) does something else.

But regardless, thanks for the help anyway.

[timboréale]

This is a very basic and clearly understandable patch (if a bit of a clever one) for someone who does understand the oscillator section and basic audio routing through the mixer stage, hence my observation. No need to take it personally - it's clearly not a matter of ownership time that brings fundamental understanding. But if you did understand the oscillator section well, this would have jumped out at you as fairly obvious, as well as the filter resonance trick which has been used since nearly the first days of electronic filters. I'm not making any judgements here - but to use an analogy, if someone didn't know how to spell the word "word" you might be a little concerned about their English skills or their literacy, and justifiably so. No shade on the individual; everyone learns at their own pace.

Anyways, to the point:

This is not a magic patch with anything spooky going on - it's quite straightforward. Attached is an image of the patch settings with the fundamental parameters relevant to your question circled in red. That should show you exactly why the cutoff, with resonance lowered, is not outputting a pitched note, but only noise, and where the fundamental pitch is, in fact coming from.

[maxter]

When using a self-resonating filter as an oscillator, the cutoff filter frequency IS the pitch. Anything that modulates the cutoff point ie modulates the pitch.

If you search "self resonating filter" on the tube you'll find loads of videos that'll explain.
Here's one interresting way of using it on the Model D:

[Josh C]

I think I understand what the original poster is trying to do. what they have done on the patch in question is created 2 layers with all the oscs turned off, filter key amount set to 64, and resonance all the way up. The layers are an octave apart. since the self resonating filter creates a sine wave, if the cutoff could be changed without changing the pitch, which it can't, the sound would not change because only the fundamental frequencies are present.  since the oscillators are all turned off, there is nothing for the cutoff knob to do except for change the pitch of the self resonating filter. if you set one of the oscillators on each layer to a triangle wave with the same frequency as the self resonating filter, then you could turn resonance down and start messing with cutoff without changing pitch. I use the triangle trick when I am creating patches with sine waves that need to be precisely in tune. The tuning of the self resonating filter is not precise enough for my taste.