Purple Brain: FM synthesis and Brain Computer Interfaces

Hi All,

I’ve returned to studying and I took a class during Fall on using brain/body signals for making or interfacing with music/sound. Our team project was Purple Brain, a series of FM synths which use a brain computer interface to modulate the tones generated. I knew next to nothing on FM synthesis, or how the brain/body works, but it was very fun to work on and thought I’d share it here.

We made a 6-operator poly synth, a 2-operator mono synth, and a repurposed version of the poly synth as a euclidean generator: basically play a chord and it arpeggiates the chord but using euclidean sequencing. The synth bit was entirely made in Max/MSP and the brain interface stuff is using Open BCI.

The brain generates signals in 5 bands (delta, theta, etc) each of those band signal strength modifies the modulation index of 5 operators which are used as modulators to a carrier operator. The frequency of each of those modulators is fixed at the top frequency those bands resonate at, eg. delta is 4Hz, theta is 8hz… Different brain bands are associated with different kinds of brain states.

So when connected to to the brain interface you can play a note and the tone modulates according to the subconscious signals your brain produces, which I think is interesting for live performance or purely for sound design. We worked with actual musicians who really enjoyed the idea.

This is a little demo song (you might recognise the chords) with the poly synth and euclidean rhythm generator:

And I made a dummy manual riffing off the DX7 and Prince’s Purple Rain. We had to submit documentation so I thought this was some tongue in cheek fun:
PurpleBrain-Operators-Manual-small.pdf (588.8 KB)

We are working on a video to demo it better.

It would be cool to keep working on this idea in the background. Maybe some of you have suggestions on improving how the FM works? There are other ideas we would like to implement written in the manual. Friendly critique very welcome.

I doubt it is a commercially viable product because brain computer interfaces are not cheap to buy or easy to use, but could have some niche users. I know there are already musicians working with brain interfaces and other body signals.

I’m really curious though, is anyone else on this forum working on novel interfaces to sound and music production?

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