There's a four-disc Castle Communications CD compilation set called Irish Folk Favourites, MBSCD. 404, contents of which are "licensed from Transatlantic". Disc 3 of this set starts off with 11 tracks by the Grehan Sisters:
Victoria, On the Gallymore Mountains, Jigs (Gallagher's Frolics/Leitram Jig, The Lake Of Coolfin, The Fairy Boy, The Black Velvet Band, Lonely Banna Strand, My Uncles In The Dail, Tommy McDonagh, The Donegal Reel and The Wexford Massacre.
It's stirring stuff, and I too would love to hear more of their recordings... now that's what I call real voices!