Spline Synth

The synth uses splines to modulate envelope parameters which produce organ like timbres. There are four oscillators each with their own envelope corresponding to each voice of the synth. Crossfades are used to blend the output of the oscillators together into a mono signal which is then processed with a delay and feedback to create a stereo effect.


Module Function Performance
Spline Synth 4 voice MIDI synth splines control envelopes
Pseudo Stereo create stereo effect
from mono input
buttons knobs

Spline Synth



Input Signal Range Notes
MIDI notes 4 voice polyphony



Signal Range Notes
-1 to 1 Mono out to Pseudo Stereo.


[Knob, Button] Function Notes
image Spline frequency envelope per voice
image set Q ladder filter
image Enable/Disable ladder filter
image cross fade voice mix
image set oscillator volume pre filters
image set wave form oscillator per voice

Version History

Revision File
1.2 Spline Synth v1.2.audulus (429.6 KB)

Pseudo Stereo


Input Signal Range Notes
image -1 to 1 audio from Spline Synth output.

Output Signal Range Notes
image -1 to 1 audio out to speaker.


[Knob, Button] Function Notes
image stereo effect enable disable
image fine knob control enable disable
image set stereo width symetrical
image set delay time for both channels
image set feedback for both channels

I am enjoying the panel design and stereo effects! Is there any reason I couldn’t just delete the midi keyboard node and turn it into a synth voice. I also really dig the various splines, and will probably repurpose them in some other patches :slight_smile:


You can do whatever you want with it, I created the synth in an attempt to try to make a sound with more of an analog timbre by introducing a certain amount of pseudo randomness into the patch. I like to use my Audulus patches within the context of the other apps on the iPad in a setup so having a MIDI controlled setup fits this mode for me.

I found working in mono and then creating a stereo effect at the end was much less resource intensive and complex versus trying to incorporate stereo effects all along the sound path.

I used @jjthrash program along with creating snippets of high frequency sound to generate the splines. At some point, I’ll try to automate a process for creating a spline based wavetable synth as the flexibility of Audulus would allow for some useful options versus existing wavetable synths.


I would also say that my patch isn’t very modular relative to the original patch used to create it because I had to rearrange the patch in order to have access to the controls in the limited space in the current patch. This is a hassle and definitely makes the design and flow of the synth more opaque due to trying to develop a particular GUI I’m after.

In many respects, Audulus 3 is like a database with poor report functionality. The reports would be analogous to the user GUI and the database would be the natural programable flow of a patch. Hopefully at some point Audulus will have the ability to create references to different parts of a patch at whatever patch/subpatch levels so any number of GUIs could be created for a particular patch rather than having to restructure the patch in order to create a particular GUI design or vice versa.

The current functionality is a kludge as form isn’t following function with respect to GUI design as Audulus 3 is almost exclusively oriented towards programming patches versus a GUI where only a limited and selected portion of the underlying patch is presented to the user.