Here's a set I played with it. https://youtu.be/nKFK_OhQv3k (Wireless soft-pot controller as well as wireless "hat" controller that uses accelerometers)

And here is the recent design of a rotary magnetic bow wheel with balanced irrational angled arrangement of magnets to reduce harmonic locking. https://www.instagram.com/p/Cr4ZXGztY27/

Here's the OSC Rotary Magnetic Bow code... https://github.com/spDuchamp/OSCRMB

And here is an album made autonomously using an algorithm built in Puredata to control the bow based on the output sound in a feedback loop. https://stefanpowell.bandcamp.com/album/autonomous-drone-lul...

Here is an autonomous recording session... https://www.youtube.com/live/LpQBtJmrez8

>This is one of the Synth's eight motor oscillators. It can produce four distinct waveforms - the optical disc creates sine, saw and square waves through reading wave reflections via infra-red sensors while the electromagnetic pickups at each motor's base produce the inductive "M" waveform.

The picture shows a small motor driving a physical "strobe" disk printed with 3 different patterns, which are read by optical sensors to create the electrical sine, saw and square waves whose frequency depends on the motor RPM at the time.

The electromagnetic pickups at the bottom of the motor apparently generate an "M" shaped wave as the motor turns. This is the one that's conceptually similar to the original Hammond organ starting from 1935 which also did mechano-electrical waveform synthesis.[0] Although the Hammond motor ran at constant speed synchronized to the power line frequency. The Hammond had a metal disk for each note of the musical scale, precision machined like gears so each note would be at the proper pitch, and the lobes of the disks create the periodic magnetic induction to the pickups which generate the repetitive waveforms.

Definitely not a desktop instrument, a Hammond can be as big as a desk itself, and even heavier. But it was a true synthesizer.

It was also in the 1930's when Hewlett & Packard started up and developed their electrical frequency generator, where a single vacuum tube triode can be wired as an oscillator and used as the source of precision waveforms at a frequency of choice. Making it directly possible for someone to construct a fully electronic organ along the same lines. A musical instrument like this would be a more modern milestone.

So about 20 years later once the patents on these type circuits expired, Thomas organs began to appear in the 1950's where each note had its own triode, so it was a very early organ which was truly a fully electronic synthesizer.

Still didn't sound as good as the Hammonds, but Hammond had decades of absolute top continuous improvement in engineering by then.

[0] Also somewhat analogous to a crankcase position sensor on an internal combustion engine.

https://en.wikipedia.org/wiki/Tonewheel

OK, motors could have spindle play and other imperfections that could make the optical disk tumble a bit and introduce phase effects. Or, as WalterBright wrote, there could be resonances between the motors. Yet, all this tight feedback makes them control the acceleration and deceleration tightly. There is nothing analogue to how these motors are driven. Not an old motor spinning up at its own pace, it's all pre-determined by the motor controller. The motors precisely follows the pre-determined speed curves, from what I hear, similar to how a digital oscillator will. Plus, the envelope is digital anyway.

One of my first thoughts was: Cool, so I can touch the oscillators and skew the pitch! No, I can't. First, there's a cover. ;) But I guess the motor controller controls the pitch so tightly that the effect would not be musically interesting. Compared to when you put your finger on a vinyl deck, for example, which has much larger mass and often a much slower motor control, leading to these slow glides.

Apart from the fancy looks, I really wonder which interesting new soundscapes this instrument can make available. To me, this looks like a "normal" oscillator with ADSR control, just re-labelled as acceleration and brake parameters.

The only other boundary condition on the function is that we want to parameterize it in a way that is comprehensible and pleasant for humans to manipulate. I would suggest that a simulation of this synth would be superior to the synth itself in every way. If you were clever enough (or masochistic enough) you could even build in "flakiness" and "parts wear" and "thermal variation".

If you really want an analog sound, then get an orchestral instrument, or an electric guitar! I don't understand this half-measure of "use-machines-to-synthesize-sounds-but-not-THAT-way".

Edit: to be clear, I like the sounds. I just think DSP beginners learn early to watch out for aliasing in their algos and have the side effect of rejecting timbres that are in any way reminiscent of aliasing from their toolset.

[1] https://vimeo.com/90101413

Also, use the fingers as a break for low frequency modulation.

The idea is brilliant as a novelty synth. Remains to be seen if it's actually useful and expressive enough.

I suspect it's a cheap trick to fool people who associate bad old recordings with vintage sound.