lately i tend to have the radio on ...
otherwise i have a cd playing which i know really good ... when there is some new music i tend to stop coding and listen to the music ... when its already known it just brnigs me in the mood .. and makes it easier to ignore any sounds from the environment (playing kids outside, wailing cat inside, wailing gf on the phone, ....
(wen i was younger i never could convince my parents that music really helped me concentrate .. but my grades convinced them enough to let me listen
)