I find that music helps me a lot to concentrate for hours at a time. During my commuting in the train it's much necessary not to be distracted by people talking. Even at home at night when there is no noise I sometimes use music to concentrate more.
I've noticed the music I listen to varies greatly. But the genre of music I listen to is always the same for the same mood.
Pop music, hip-hop, rap, electronic music (110 to 130 beats per minute): very often. The most important thing to keep focused on my work is to listen to the same CD in loop for hours. Examples: Alizée, C2C, Eminem, Hopsin, Flo Rida, MIKA, Rhymester, Stromae, The Black Eyed Peas, The Flaming Lips, Zaz.
Slow music with beautiful voices, classical music: when I'm a little tired. Examples: Bach, Chopin, Moricone, Stravinsky, Vangelis, Yael Naim, 分島花音.
Electronic dance music (over 150 beats per minute): when I'm really tired. Sometimes I should be sleeping in my bed but there is something urgent to do (The server is down!) Examples: Kap Slap, Klaxons, 田村ゆかり.