Window transform module (WTF?)


Hey everyone!

So I was watching this DivKid video on a prototype module that’s essentially a PWM-able crossfader between two wavetable OSCs (as far as I can understand).

It seemed intersting enough sonically so I thought I’d try to achieve something similar in Audulus, since the idea is pretty straightforward in itself. I figured you could use any two oscillators as the soundsources as long as at least one is synced to the crossfader. This is as far as I got.

Any ideas on how to do this in a more elegant way? Also, I couldn’t figure out how to slide the transform window back and forth. A delay before the crossfader, maybe, but that just seems kind of awkward. I’m sure someone here has a neat expression in mind that will do the trick. I myself am somewhat mathematically challenged…

Any thoughts on this?

WTF sketch.audulus (31.4 KB)


This might be similar to what you had in mind uFSK Frequency Shift Keyed Dual Oscillator


This is a very cool oscillator! Also I think you really nailed it in a cool way in your patch. You can actually do a little more in that you can add multiple different points instead of just one or two.

As far as this:

I’m not sure what you mean? This seems to behave exactly like the video, except it lacks a few of its features like the noise and the DC, which would be easy to add now that you have this structure.


I started work on replicating this about two months ago, here is my test bed.

single dual window oscillator.audulus (20.5 KB)

Oh yeah, and I nearly forgot I have a uWindow utility for making waveforms like this that I made for the uModule crazy of 2017.

uWindow demo.audulus (21.2 KB)

Window Transform Utility.audulus (28.6 KB)

Ok, I reworked the testbed to be a utility like the uWindow. I should point out that the front waveform really wants to be a sawtooth wave for it to work exactly like the WTFO, but sonic results are similar. If you really want an exact recreation, I’d be happy to help out. In the meantime, you should have lots of fun sticking any two waveforms in there as mucking about.


After watching the video again, I see that the WTF doesn’t use quite the same approach as the uFSK. Since the uFSK also switches between two oscillators at audio rates, with a suitable FSK signal it could produce an output similar to the WTF output. The internal FSK signal is currently a square wave derived from the zero crossings of oscillator A, but it would be fairly straightforward to modify it to produce a variable single or dual “window”. By providing an option to use different external “FSK” waveforms for the switching signal it allows a mix of the two oscillators rather than a hard switch from A to B. I should probably add straight A and B osc outputs, which would make it easier to derive a synced FSK signal


I think it’s a matter of using an internal phasor to make the windows pretty. From there it’s just designing waveforms that are interesting, I think there is also pitched random steps the the oscillator.


Phase modulation of the window position was the word idea I was looking for. Found a phase modulatable phasor in one of Robert’s patches, that seems to do the trick. This creates a nice ripple effect of the harmonics, and some nice wobbliness in the pitch, depending on inputs.

As for offsets and noise, it’s just a matter of what you plug in. I was going more for a general utility module, not just an oscillator with a fixed set waveforms.

Thanks everyone, I’ll do some more playing around and report back.

(On a side note, I wrote the opening post using safari on my ipad. Not a pleasant experience with all kinds of dynamic elements jumping around on the page and the keyboard covering the text box half the time. Does the forum have a “mobile mode” or something?)


Caring is sharing. If you make something fun, we’d all enjoy seeing it. :nerd_face:


Keeping my eye on this thread. @stschoen’s uFSK is one of my favourites. I almost feel like there should be two branches here. On the one hand, some tinkering with the uFSK just to explore some new ideas; on the other hand, some approximation of the WTF Oscillator from the ground up.

Once again though, we can really see the need for a proper scope in Audulus 3. I suppose the engine has created some complications. When it finally does get made in 4, it would be a good idea to have multiple iterations of the scope in order to really nail it. Tiny scopes, and full featured robust scopes.

On a side note, has DivKid ever tried out Audulus? It would be cool to see him review one of @stschoen’s or @robertsyrett’s ‘modules’!


He is aware of it but he has so much gear that he has to demo, it’s actually kind of impressive that he also has a full time teaching job and a child. And I am pretty sure that pile of boxed modules will always take priority over iOS stuff.

It’s up to us to show the world how to use the ES-8 with Audulus and Eurorack!