There are a couple ways for a solo performer to play multiple electronic instruments at one time. The most straightforward way might be using two (or more) keyboards, either playing one with each hand simultaneously or quickly switching between them, maybe with the use of one or more sustain pedals.
Another option is "splitting," which is a feature on some MIDI keyboards that specifies a given key as a threshold between two parts. If you enable a split on your keyboard at C3, every key to the left of C3 is sent to synth 1, while C3 and above are sent to synth 2. This gives you control of two voices with one keybed, which is convenient in terms of space and arguably more comfortable, because you don't have to reach all over the place. But it is also limiting if you ever want those voices' pitches to overlap.
Yesterday I learned about this "3 Zone" technique for solo piano.
It seems to be a very old idea that this guy proceeded to coin, because I can't find references to it anywhere else. I have no piano training but maybe this is something everybody learns as a child. Anyway, this is a really nice way to think about playing piano, but it also reminded me of splitting a MIDI keyboard. It's more complicated than the technique I described, not only because there are three zones instead of two, but also because instead of splitting based on a fixed key, individual fingers are dedicated to different voices. Hitting C3 with your left ring finger could mean something different than hitting C3 with your right thumb. The piano doesn't care, but if you want those different gestures to trigger different voices, how could we capture that?
I'm imagining some sensors, maybe in a pair of gloves, that detect which of the player's fingers are in use at any given moment. If we trust that only the gloved hands are playing the keyboard, and the player's fingers are never crossed over each other, then we could map pressed fingers to pressed keys from left to right. We could route that note information to different voices on the fly based on that mapping.
I don't plan to build this system and I don't think I have the performance chops to make use of it anyway, but I am going to keep thinking about it. (If you see this and do something with it, please let me know!)