I need loud music. Music for me means the difference between 1,000 words in two hours or 3,000 in the same amount of time. Also for me music need to be loud, therefore I carry good headphones always with me.
Also I had discover that not any music works, I need different music stiles and languages depending what I am writing. If you need music to write, learn which one and for what kind of writing. In my case, I need music in spanish when I write in English and in english when I write in Spanish.
If you need no-music, try a white noise track, most likely you will discover that the result will be simply incredible.
i.e. I have playlists in the iPhone for writing, not complicated to do, but the difference is incredible. Also remember to remove those that annoy you. No need to have bad music with you.
i.e. Pay attention if you need instrumental or classic music, the orchestra and the director can change everything. I hyper focus on Beethoven Symphony No. 9 with the Berlin Philharmonic and Von Karajan directing; but not on other versions.