this may just be me, but I remember - when writing up my MA diss - being at my most productive whilst listening to drum&bass - I agree, I can't listen to anything with lyrics as I find it too off-putting, but somehow the beat/bass was very motivating! I have a VERY diverse taste in music, so it's not just that I am massive d&b anyway... but I do understand that d&b isn't to everyone's taste. Also, I found having a supply of boiled sweets or mints to suck on helped with my concentration - I always had a bag of murray mints on the go in my undergrad years too. strange.