Audulus 4 Modules


I’m doing some prep work for Audulus 4. I’d like the new library to be more focused. Instead of having multiple versions of the same type of module, there will be one of each. This will be less overwhelming, more focused, and easier to wrap your head around.

People can of course make variations - many different types of complex VCOs, for example - but in the official library there’d be one of each.

I’m looking for some input to see if I’ve missed any. I’ll probably need a lot of help building some of these that don’t already exist.

I’ll post about more types of modules soon, but here are the three basics first - VCO, VCF, and VCA. The VCA category in particular is a bit thin, so any help there would be much appreciated.


  • Basic
  • Complex
  • Wavefolding
  • FM
  • PM
  • AM
  • Crossfade
  • Wavetable
  • Karplus Strong
  • TZFM
  • Polyphonic
  • Sawtooth Wave Animator
  • Scanned
  • Additive Harmonic
  • 8-bit
  • Triple VCO
  • Glitch
  • Physical Modelling
  • Supersaw
  • Formant
  • Sample-based
  • Phase Distortion
  • Granular
  • Resonator


  • LPG
  • Ladder
  • 303
  • Multi-input (Forbidden Planet)
  • SEM
  • Synthi
  • Formant
  • Filterbank
  • Variable Pole
  • CMOS
  • SH-101
  • Resonator
  • Comb Filter
  • APF
  • ARP-type
  • MS-10
  • Polivoks
  • Sallen-Key
  • Curtis
  • Dual Peak
  • Mankato-like Ladder


  • Diode
  • Tube
  • FET
  • Digital
  • Digital Crush


Effects (reverb, delay, stutter, etc), envelopes, modulation sources, and Sequencers?


Those and many more are coming - I meant to start with VCO/VCF/VCA and see if i’m missing any within those categories :slight_smile:


Proposal for the Basic VCO.


It might be nice to include some prepackaged FM patches (piano, strings, etc). As well as drum modules, and basically all of the @stschoen synth voices.


Is that more into preset category? I’m more talking about types of oscillators and kinds of VCFs here - drums will be their own category too. You know what I mean?


Maybe ‘shape’ could control phase for the sine wave?


Maybe better control for the FM/PM oscillator? I’m assuming the FM oscillator will have some more advanced controls there for it.


I just think that driven sine wave is already pretty close to a square wave. Perhaps it could crossfade with a fully rectified sine wave? That has a different harmonic spectrum and can be found on synths like the Pittsburgh microvolt 3900.

Give me a minute and I’ll reverse engineer it.


That’s a good idea!


Transistor Ladder Idea


rectified sine wave scaled and in phase.audulus (19.5 KB)

It took me a second to figure out how to make a rectified sine that was in phase with the original and didn’t shift up an octave. This should lead to minimal phase cancellation over the course of the shape knob. Of course phase cancellation and shifting an octave up could be useful as it gives you a half-rectified wave when shape is in the middle.


My understanding is that transistor ladder topologies are just low pass filters. But a multimode filter is a great idea.

Also the CP3 mixer is really specific. Will inputs with nothing in them act as dc offsets? Will there be the characteristic asymmetry between positive and negative clipping?

edit: duh, didn’t see that note for some reason


Yeah electronically probably, but it’s easy enough to extract the other filter types digitally. I’m not even sure if APF is possible, but I’m thinking this type of look to the module would be the template for all of the filters (if it doesn’t up the CPU% too much).

Thanks for the rectified sine btw!


I suppose “transistor ladder” could be switched out for “musical resonant” to get the idea across. The important thing is it should be able to track the keyboard, respond to audio signals musically in both the audio and mod inputs, and self resonate without whiting out the cord. :rofl:

My pleasure. Always good to shape some waves before bedtime.


Idea for VCA


Here are some simplified versions of these modules for total beginners and/or times when simplicity is all you need!


Although Robert is correct in describing the typical ladder topology as a low-pass, it is certainly possible to build other filter types using the same topology. I’m not sure how useful they would be. Here’s a multimode State Variable filter as well as an all-pass filter, both from Zavalishin’s work. uAPF V1.2.audulus (34.4 KB)
uSVF V1.1.audulus (33.4 KB)
You would probably want to re-skin the underlying modules to fit with the overall aesthetic.


One of the big differences between the built-in VCO and the roll-your-own variants we’ve built from phasors is the anti-aliasing embedded in the node. Any thoughts on how that might change in V4? A lot of the VCOs you’ve suggested would be difficult to construct efficiently using the VCO node.


Taylor mentioned that we might introduce supersampling to Audulus 4 to address this. That way you could make an oscillator of whatever shape you want and have no aliasing at all.