[Visirale]

I saw a live video of Radiohead's "National Anthem", and their electronics guy plays a keyboard instrument. It has a normal keyboard layout and all, but it has a string in front of the keys. When he carresses the string in different ways it changes the sound. I've been looking for a new strange instrument to add to my collection... Any idea what this thing is called?

[LWatford]

It's an Ondes-Martenot. Here is a link to a page about the instrument.

Here is a modern counterpart. It isn't quite the same, and it isn't quite "modern," as it uses CV jacks instead of MIDI. This is the model Jonny tours with, rather than his real version (though he's used it occasionally).

Here is a link to buy a French Connection, and you'll also need a synth that will accept CV outputs.