Why is it that no one has produced a convincing rock novel? Or, at least, I sure haven't read one yet. This article (Resisting the rock-novel demon) seems to suggest that authors and readers just don't get the rock and roll lifestyle. I think it may be difficult to capture every aspect of what it is like to be a musician, let alone pull of the sense of build-up and let-down that comes with it, but there's no reason that a character can't have a "career" as a musician, just as he might a street sweeper. It is part of who he is, helps to determine how he views the world.
Or maybe it's just that the novelists that have attempted it are merely trying to live out their own rock n'roll dreams. Or the article suggests this:
A criticism that has often been levelled at the rock novel is that, because the literati are largely upper-middle-class, they haven’t ever experienced the struggle and graft that go with dreaming of a headline slot at Glastonbury. This is almost certainly rubbish, partly because the middle class has just as much historical right to comment on rock existence as the working class, and partly because musicians are, on the whole, roughly 13½ times lazier than novelists.
I'm not sure what that has to do with anything (or what it has to say about writers who are musicians).