A demo where a pixelated image gets progressively unpixelated when you play a musical password in the right order.
See demo video here: https://www.instagram.com/p/BYTtqZYhblC/
There's a debug mode that shows amplitudes being detected for each frequency band. Set "debug" to true in the code. Please note it's tuned for a certain kalimba. I guess if you want to use it with a different instrument you'll need to tune it again.