... something with a hard driving bass for timed 5 to 10 minute games. Music with power and zero lyrics.  Chanting or a story line are  distractions; no matter how simplistic the vocal message. 

I've been enjoying really upbeat bop jazz (like Charlie Parker or Coltrane)- keeps the adrenaline up!

I usually have the tv on Super Sweet 16.  Spoiled rich kids bitching at their parents helps me concentrate. 

I almost always have music on whilst I'm playing chess online. It's usually rock/metal music but sometimes classical, folk and pop. I'm not sure if it helps of not but I don't find it distracting :)