I don't listen to music at all now, but it occurred to me that when I worked as a tech writer at a software company, I had no problem with my office mate playing something in the background, and in fact usually enjoyed it. (Except for the Nancy Sinatra debacle, during which I got to hear Nancy Sinatra and Lee Hazelwood serenade each other for probably close to four hours! :)
Once it came time to do any tech editing, however, I had to have quiet. That trend has continued now that I'm working as a full-time copy editor. My husband, who sometimes does his functional programming from home in our shared office, uses noise canceling headphones to listen to Queen or Kraftwerk or Pink Floyd so it doesn't disturb me.
But what is it then about tech writing vs. editing that makes it so different for my concentration? Perhaps it was the fact that putting the instructional sentences together from design specs and working with the UI required less focus. My husband's functional programming, though, would seem to require a LOT of focus I would think. So maybe it's not solely that.
I do know that I'm definitely a listener of lyrics. They get in my head and I memorize them inadvertently and unwillingly. My husband--definitely NOT a listener of lyrics. So instrumental-only music usually is sort of okay with me, but once there're people singing words, it's right out the window with my train of thought.
My guess is it's a combination of various factors, and not solely difficulty level of the task, and like Carol Saller says, I don't think it's only ALL aural or visual either. The brain surely is still a marvelous mystery.
How do you feel about music in the background while writing/editing? Feel free to comment!