I’ll volunteer The Nylons - a favorite group of mine for many years now. 
Lion Sleeps Tonight
One Fine Day
Heavenly Bodies
Me and the Boys
That was sublime. Although not all the instruments were stripped away on every song; they were pretty minimal though.
It’s rather like crediting “Revolution (Nike commercial song)”
Pentatonix has done pretty well doing covers on youtbube (Evolution of Music - Pentatonix - YouTube).
Delta Rae has some pretty good harmonies as well (Delta Rae - Bottom Of The River [Official Music Video] - YouTube).
I have heard “The Bard’s Song” before, but not like that. That’s great! Thanks!
Mr.Me
46
Hey Ocean! from Vancouver do some nice harmonizing.