I think it's probably down to each individual. I find it actually helps inspire me sometimes, set the mood for what I imagine a sketch could eventually become. I also find painting without music to be difficult to focus, a lot of people need background noise to work, even if they eventually become completely unaware of it.
DO WHATEVER WORKS FOR YOU. Sorry about the all-caps, but I've been through shouting matches on and offline about this before...
There are some people who work better without music. There are other people who work better with music. The problem is that some of the people who work better without music insist that everyone must work better without music, much to the annoyance of those who work better with music.
I'm one of the ones who works better with music. And I know, because I've tried both ways. Without music, I get too easily distracted by petty background noises or my own background thoughts. The right music can occupy the part of my brain that would otherwise distract me, so the rest of my brain can focus.
Also, I live in the city, so there's a constant stream of background noise, some of it extremely annoying and distracting. Music is often the only way to block out those noises. (Car alarms. Screaming infants. Screaming hookers. Fresh Direct trucks. Small children on pogo sticks right under the window argh argh argh...)
Plus music gives me drive when I'm tired or lacking motivation. I even use it as a reward system to help me get through my work by reserving favorite playlists for work only - that way, if I want to hear my favorite music, I have to work. On some projects music was the only thing that got me through the job...
It will be different for different people, of course. Some people find music too distracting and are better off working without it. So again, try both ways, do what works for YOU and the hell with contrary advice.
It can be a good idea generator, but I sometimes find it distracting, especially when trying to execute an idea that's created by the music i'm listening to. Then there's other tunes that simply fit well with the act of drawing and make it more fun; I really enjoy this one.
I like something to listen to, otherwise I listen to my brain and my brain is distracting. Also, it's kind of lonely when it's too quiet. I like television (Something steady like documentaries or dramas, where you can follow the gist of things without having to actually *watch*.) or talking podcasts like radiolab and similar.
If I find I need to concentrate extra hard on something, I just pause the player for a bit.