Creating mood lighting for LEDs based on key of background noise or "music". Traditionally sadder keys are more blue, like Dm/Am, while C is happier and more green, yellow, etc. Next steps for the project include creating a custom PCB and sell it on obscure subreddits.
The bulk of the project is not hardware, but programming key/mood detection. While chord detectors already exist, tailoring the timing for my purpose, minimizing background noise, then assigning a key/color was still a stupid amount of work to get right. Email me for Github repo.
The build itself is really simple, and the next goal is to modify for connection to color channels on LED strip lights.