Why is it that when people sing their accents go away or stuttering disappears?

I don't think the bit about accents is actually true. I know that the distinct Yorkshire accent of the singer of Arctic Monkeys sounds different from the unmistakable drawl in most country singers (Or is this just a perceived difference in accent due to the fundamental difference in their respective genres?). But it does seem like accents get blurred, at the least, when you sing.

The bit about stuttering might have something to do with the fact that you know exactly what words you're gonna say. When you're just talking, you're translating the thoughts in your head into words on the fly. But I don't know much at all about this speech impediment, so don't quote me.

Singing and speaking use slightly different areas of the brain. For that matter, so does speaking in different languages. I knew a stutterer who could speak flawless French.