http://youtube.com/watch?v=IIwbB-nKEpE Alright, this is a Muse video, but only pay attention to the beginning (it's a live performance). Matthew Bellamy is doing a tremolo on this thing after the strings on his guitar. As you can see, it lights up as he touches it and it makes this very interesting noise. What is that? Does anyone know what that is? Are they on certain guitars, or can you attach them, or what?
That's an XY pad. It alters the pitch and whatnot of the notes being played. XY pads are common in music editing software programs, like Fruity Loops. It just so happens he had one installed on his guitar. It's obviously custom.
I saw that on TV a week ago I think. It was a different live show, though. But it looks and sounds awesome.
Matt has a buttload of effects built into his guitars, if you look at them there's like 10 different knobs on them. I think the company that builds his guitars is called Manson guitars, and Matt just likes having effects built in rather than having a ton of pedals onstage.