A huge issue I've had trying to find music/noise that I can use to drown out background noise is the human voice. I can't find a playlist that has sounds/music without human voice! I found a couple great trance songs that just let me put my head down and really tune everything out... and then there is either a sample of a lyric or even a "hey!" added in for no reason and it pulls me out. And if they don't have a human voice, often it will have some other repeating noise that pulls my brain away from the task. I put on headphones to keep my mind from procrastinating at a time when it really, really wants to. The hardest thing is finding music/noise that doesn't give it any excuse to wander.