Intro: Mini Synth - Atari Punk Console Mod
It's surprising how much I could fit into such a small space. I considered using LDR's but decided against it as this would prevent me from playing it in the dark.
Second half of the video the synth is running through Autotune playing C minor scales. You can also target the Autotune notes via MIDI keyboard and use the mini synth as a sound source.