Spline Synth

Paulinko · September 6, 2018, 1:59am

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.

Overview

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

Input	Signal Range	Notes
MIDI	notes	4 voice polyphony

Output

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

Controls

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

Version History

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

Pseudo Stereo

I/O

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

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

Controls

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

robertsyrett · September 6, 2018, 7:14am

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

Paulinko · September 6, 2018, 1:33pm

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.

Paulinko · September 6, 2018, 2:08pm

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.