I've been on a massive kick of using composite video in creative ways, such as this old digital composite mixer I bought off clist. It has two selectable and transitionable video streams, so if you patch one of the outputs to one of the inputs, you get some real weird stuff.

Here I'm keying out dark colors with the panasonic wj-mx30, then feeding output 2 back into input B. By setting the transition all the way, but still having portions of the screen not keyed, you get this weird effect. It's really awesome and trippy, and lots of fun to do things to the beat of the music.

I hope you enjoy!