Barbara Dickson went from Folk music in folk clubs, to mainstream success in the pop charts and in musical theatre, then back to the folk music world again. Good on her I say. Don't see why you can't do both. Let's face it Karine Polwart chops and changes from album to album. Why not??? If you make a good folk album then it is a good folk album - even if the previous one was a cover of 80s pop songs or whatever. Why should musicians be restricted?