If it's a tape you have, It might also be the original Ceili's Muse release, "One Voice." Ceili's Muse was initially a duet comprised of Mary Maddux and Stephany Bingham (later Stephany Freeman and later still Maggie Drennon), which became something of a minor legend in the Houston celtic/sca scene during the late 80's, early 90's. I don't recall that there was ever a CD pressing of "One Voice."

Mary and Stephany traded off singing duties, while the guitar was almost all Mary. (I have photos somewhere of Stephany holding a guitar and looking very silly with it.)

If the version you heard was heavily produced with a lot of reverb, it's the "Dark Lady" version with Maggie singing (released in 1995, after the duet split and Maggie took the name). The "One Voice" version is much simpler, with a more complex voice ... that's Mary.