Good music is important for me to get into "deep hack mode". Usually, it's house, trance or something like that. One day last week though, though I had David Wilcox's "Do the Bearcat" on repeat for about 2 hours. It was the most productive 2 hours I've had in a month.
The internet radio stations I listen to for programming music require each mix (song) to be between 45 and 90 minutes, not fade or do other distracting effects, and a couple other basic rules that make it quite good for programming.
I'm actually trying to make lists of the best programming music now. First, I'm collecting databases of all the music I can find. The electronic genres are the most elusive... I have a database listing about 16MM tracks and mixes now. Once I get all that I'll finish making those lists.
I have found some decent web stations, but for the most part I just rip hundreds of tracks from dozens of stations at a time and pluck out the couple good songs and then repeat.
Who would have thought?