a web search came up with surprising info that Paul Winters also recorded this song as Sweet Comaraghs But I see from a listing of artists on the album that Karan Casey probably did the singing. Verified by this item:Celtic Solstice reviewed by Diana Lomonosova
""A Chomaraigh Aoibhinn Ó (Sweet Comeraghs)," the seventh track poetically illuminates, 'Cliffs and steep slopes in every direction,/ Like a satin weave from a magic loom,/ As the dew falls from the heavens high,/ Sweet Comeragh.' Casey's voice weaves a tapestry of the majestic Comeragh Mountains in County Waterford, Ireland. I dare you not to heave a sigh of pleasure while listening to her!"

Real Audio on a compilation album I didn't listen to it and don't know which singer is featured.
Solas on this archived radio programme looks interesting

Also, the song has been recorded by a singer I've never heard of Zena