Music to listen to when concentrating on a task. Recommendations welcome

First my recommendation: go to Grooveshark.com and do a search for FSOL, select Lifeforms (disc) 1, then choose all eight tracks from there to listen to if you have something to concentrate on and have a lot of distractions in the background or just prefer to have music on while doing something important. For disc 2 do a search for something along the lines of Future Sound London Lifeforms disc 2.

It's tricky to get just the right mix for concentrating on a task as Lifeforms has, as:

1) one song won't do, as it ends quickly and then you have to find another. Usually a 30 minute+ range is needed
2) singing tends to disrupt concentration (especially if you're working on a language-related document like translating or proofreading), unless it's impossible to understand or just chanting
3) go too ambient however, and the music will be incapable of drowning out annoying background music. There has to be some overall rhythm and flow to the music.

If you don't feel like using Grooveshark you can see a quick sample here of a few minutes.





So, any other recommendations?