What the oscillator is actually doing
A fractal like the Mandelbrot set is a rule applied to a point on the complex plane over and over. Some points stay bounded no matter how many times you apply it. Some run away to infinity, and how fast they run is a number you can measure.
Laura takes a path through that plane, samples the escape behaviour at every step along it, and uses the result as one cycle of a waveform. Move the path and the harmonic content moves with it. A wavetable synth plays from a stack of frames drawn in advance and blends between neighbours. Laura has no stack. Each time the path moves, it works the cycle out again from the fractal and blends the new one in over about 10 ms, so the change doesn't click. Any point on the plane gives you a cycle, and nobody had to draw it first.
Six kernels ship: Mandelbrot, Julia, Burning Ship, Tricorn, Multibrot and Newton. They are not skins on one algorithm. Each has its own escape behaviour, so the same path through Burning Ship gives a harsher, more asymmetric spectrum than it does through Mandelbrot.
The boundary is the instrument
Sample deep inside the set and everything stays bounded, which gives you a smooth wave with very little going on. Sample far outside and everything escapes immediately, which gives you close to nothing. All of the detail is in the thin, infinitely complicated region between the two, and by hand it is easy to miss by a pixel.
So there is a control that does not let you miss. Boundary lock pins sampling to the edge of the set and keeps it there while you move, and a second mode traces the coastline itself and uses that trace as the wave. A position control walks you along the edge. It is the difference between owning a fractal oscillator and being able to play one.
There is a longer piece on how this sounds in practice: what does a Mandelbrot set sound like, and a follow up on playing the edge of the set with modulation driving the position.
Three ways to hear the same slice
Reading the measurement straight off as the wave is the obvious way to do it, and it has a sound of its own. Escape values sit flat for most of the path and jump where it crosses the edge, so the wave is mostly a few sharp spikes, and spikes buzz. Every fractal patch ended up with some of that buzz, wherever you pointed it. So each oscillator has a READ tab with two other ways to hear the same slice.
Spectral turns the slice into a spectrum. The brightness at each point along the path sets the level of one harmonic, so wherever the path crosses the edge you get a formant peak, and moving the path moves the peaks. One knob sets how many harmonics the path is spread over, from 8 to 512.
Phase keeps a plain sine and uses the slice to push its phase around, the way an FM operator does. Depth sets how far. Ratio runs the fractal 1 to 8 times per cycle of the sine, and Tone goes one way toward a warmer, rounder version and the other way into operator feedback, brassy and then close to a saw. At low depth it's a sine with a little fractal grit in the overtones. At high depth it's dense and metallic.
Wave, the original reading, is still the default, and patches made before Read mode sound exactly as they did.
The coordinate is a modulation target
The point in the complex plane that all of this reads from is an ordinary destination in the modulation matrix. A macro can push it, an LFO can circle it, and a chaos attractor can wander it on a path that never repeats. Because the orbit does not repeat, the note does not repeat either. A held chord keeps finding new harmonic material for as long as you hold it, without a single automation lane.
That is the part that tends to sell it in a demo and the part that is hardest to describe in writing, so there is audio below.
Hear it
Showcase
Two minutes, every part played by Laura, no other instruments.
Psytrance
The same synth doing one job properly rather than showing off.
Read mode, one preset at a time
Short phrases on the factory presets built for Read mode. No effects added after Laura, and nothing in them but Laura.
Seahorse Choir · Spectral
A pad. The path drifts across the seahorse valley, and the formant peaks drift with it.
Hollow Reed · Phase, Ratio 2
A lead with only odd harmonics, over a quiet Seahorse Choir bed.
Phase Tines · Phase
Electric piano comping. The filter envelope does the strike, the fractal does the tine.
Formant Walker · Spectral
A lead at a low harmonic count, so the fractal's bright runs land where vowels would. Hold a note and the vowel moves.
Harmonic Weather · Spectral and Phase
Two oscillators reading two fractals two ways, with slow LFOs on both. Nothing in it repeats.
What it is not
It is not a novelty bolted to the side of a normal synth. The fractal engine sits in the same oscillator slot as wavetable, FM and classic analog, through the same filters, the same sixteen slot modulation matrix and the same eighteen device effects rack, so a patch can be one part fractal and three parts ordinary.
It is also not a research project you have to learn maths to operate. There is a canvas, you drag on it, and you hear where you are. The boundary lock exists precisely so that the interesting region is the default rather than a reward for patience.
macOS and Windows, signed installers, no account. Buy Laura for $69 when you are convinced. One payment, lifetime license, free updates.
Questions
What is a fractal oscillator?
An oscillator that derives its waveform from the escape behaviour of a fractal rather than from a stored wavetable or a mathematical shape like a saw. Laura walks a path through the complex plane, measures how the fractal iteration behaves at each point along it, and reads that measurement as the waveform for one cycle.
Which fractals does Laura use?
Six kernels: Mandelbrot, Julia, Burning Ship, Tricorn, Multibrot and Newton. Each has its own escape behaviour, so each gives a different family of harmonics from the same path.
Does it sound like noise?
Not on its own. Sampling deep inside a set gives a smooth, almost sine-like wave, and sampling outside it gives silence. The interesting material is at the boundary, which is why Laura has a control that pins sampling to the edge rather than leaving you to hunt for it.
Is this the same as an FM or wavetable synth?
No, and Laura has both of those too. Wavetable, FM, classic analog and fractal are four engines in the same signal path, and a patch can use any of them per oscillator slot.