I'm almost incapable of writing without music, especially when I first sit down to start for the day. It's like I need the ... I dunno, the distraction? I need something to put one part of my mind on so it'll get out of my way and I can start writing. I swear I don't have ADD because that need doesn't show up in any other part of my life, but unless I have music to divide my attention, I can't settle in to write. It's like part of my brain is a little kid. "Here, listen to this while Mommy works."
Once I get started, and especially if I fall into the hole, it becomes less important. But starting out for the day? Yeah. I need it.