Animaterra, also in the surf-music category too (Beach Boys are a prime example). Isn't this more from the a capella style of singing (or 'barbershop quartet' style too)? More recently, Jimmy Somerville and Michael Jackson sing the same way.
I sing like that sometimes for backing/harmony - WyoWoman, is this likely to be damaging my voice? (I won't ask, "Should I stop?", bcos anyone who's heard me may be biased... ;-)