If I’m writing fiction I prefer silence. Otherwise I am too distracted: by the music, or the lyrics, or the resulting imagery. My mind starts wandering off on unhelpful tangents. For non-fiction I occasionally put the radio on, fairly low, so that it’s background noise. It keeps my parrot happy and I don’t have to get up and change CDs etc. When I listen to music I like, I prefer to give it my full attention. And the same goes for when I’m writing, or reading: full, undistracted attention.
I’m wondering if this is partly due to growing up with a deaf father. We had to choose between conversation and the radio, or the tv. His hearing aids only let him hear one lot of sounds at a time, so we rarely had the background noise of radio, television etc, that I knew existed in my friends’ homes.