The right choice of sound background for programming sessions can be essential, especially if they just go longer than 1 hour straight...
Imagine youre spending time to explore Django Possibilities, Hack yourself a new Typo3 Extension, or adding a new Kernel module for your favorite no name, cheap pcmcia Wireless LAN card...
Doing that straight for 6 hours or a longer ammount of time, you need to overcome sleep, avoid being disrubted by too rocky music, or too many spoken words.
Whatever some peoples might say, the best time for coding is the night, hence youre not disrubted by phonecalls, or outside influence like social stuff, thus the music needs to be good to listen too even at low levels of volume, one could always turn over some headset or earphones, but in general having earphones on your head for longer than 6 hours, believe me, is not a good idea.
I'm myself a big fan of three main „categories“ of music for coding.

1. i usually start with something rather energic, like demoscene radio, it is noisy, without being disrubtive, besides im a sucker for oldschool computer stuff (collecting those old boxes myself...)

2. when the hours pass by, i slide over to last.fm, and search for the term chillout, shows you a whole new listing of good music, thats not as noisy as demoscene radio, but rather relaxing.

3. Last but not least, i switch over to some classic music, hector berlioz made some great operas, or go with some verdi, or haydn, operas are not as relaxing as chillout, thus wont get you sleepy, yet they tend to get my brain in a thinking state (id call it the extra push youd need for late hours or long coding sessions...)

Links:

www.last.fm www.scenemusic.eu/demovibes/ de.wikipedia.org/wiki/Hector_Berlioz de.wikipedia.org/wiki/Giuseppe_Verdi de.wikipedia.org/wiki/Joseph_Haydn