This is all about modding and tweaking the hell out of various hardware. Be it a toy synthesizer or a pro gear - there's always some room for improvement.
While circuit bending process, to be successful, generally calls for a person completely unwise in electronics, there are still some nice things that professional electronicans can do about it. That's ok that we are unable (just cannot from a moral stand of point) to short completely random circuit points with wires, as well as we do require extremely overdone reasoning above curiosity - we can still have some fun.
Synthesizer & other gear internals
Programming the vintage stuff
Technology and just some interesting stuff