Here is another little noise maker that I almost did not put on the site, but when I play it on stage I get a lot of questions about it, so....  It is your common run of the mill optical theremin. These are super fun but not uncommon. They are super easy to build and I think everyone at any level of soldering should at least once in their life. schematics and kits can be found just about anywhere and really the largest differences you will find between them are the cases they come in.