Warning! This project may have nutty content. All the circuits work, but some of techlib's projects are just for fun and don't necessarily represent the best way to accomplish a task. I usually explain why in the text, but many people don't read the text, at least not carefully. So, if you see the nut, remember that the project is likely to contain nutty ideas.
Picking up hum to use as a timing reference is pretty crazy. It works and I'm using it; but it's still a little nuts.
Class-A audio amplifiers are just plain nuts in many people's eyes, despite the fact that they work and are quite simple. If you're the serious type, stick with an LM386.
Using a microprocessor to punch the keys of a keyboard as a method of interfacing is, well, you get the idea.
Building stuff is fun, and nutty circuits are even more fun when they work.