A singer is certainly a musician, Ray. I think we all mostly agreed on that a while ago. And the OED's claim for 'harmony' do make things awkward, dunnit?! ;-)

The grey areas where spoken word or rhythm shades into music... I've no idea, mate. As Johnny wisely says (sort of), "It may not be to my tastes, but if you think you're a musician... You probably are!" ;-)