What is the song that plays in Naruto Shippuden when Deidara fights Gaara? I've been searching for that song for a really long time but I can't find it. It's kinda sad (?? for me at least) and it has a violin or cello or something like that.
It's called Deidara's theme. 
https://www.youtube.com/watch?v=0Kd4mOSrTh8

At 0:42, the strings start playing.