Made with a custom made digital sequencer for the Casio MT240, with one critical wire removed.
The uC is synced to the Casio keyscan via a wire that triggers an interrupt in firmware. With this wire floating (in the air, literally), electromagnetic interference causes interrupts to randomly trigger. This looks like injecting a bunch of pulses in the Casio scan detector lines at random times. Normally, the sequencer is timed to only inject pulses at scan times that only correspond to keyboard notes. But because it's no longer synced to the scan cycle, it can inject pulses at times that correspond to the UI buttons, which is why it also randomly changes instrument and triggers the drum machine. At very high clock speeds, this is extremely chaotic and fun. There's also a way to 'control' it: by physically moving your hand near the dangling wire, the random interrupt rate can increase/decrease. I wonder if this can be tuned in a way to make a sort of proximity antenna.