An iPod doesn't help me concentrate, but sometimes music does.

I've noticed lately that listening to music with headphones helps me focus more than listening to it through speakers. I'm assuming this is because the headphones make the music the only thing I hear, where as with speakers the music is just another thing I hear.

  (...) but it has to be techno I've heard before (...)

Definitely, you want the music to set the rhythm for what you're doing but not to take center stage. I don't listen to techno, but I find instrumental funk is great for this (Beastie Boys' "The In Sound from Way Out" and Forbidden Ensemble's "Porno Soundtracks" are my favorites, not that anyone asked).

    I've noticed lately that listening to music with headphones helps me focus more than listening to it through speakers. I'm assuming this is because the headphones make the music the only thing I hear, where as with speakers the music is just another thing I hear.

I couldn't agree more! My hypothesis is that it sort of seals me off in my own little world.

Exactly what I was going to write! :P I find it really easy to tune out to music I've heard before, But it has to be to a good rhythm if there is too much irregularity I'll get put off