Ever since releasing their 1975 debut, this Bulgarian women’s choir has been beguiling international audiences with their otherworldly voices and acrobatic harmonies. The country’s unique polyphonic choral tradition is full of intricate harmonic dissonances and discrete microtones—and the results here are hair-raising. With minimal accompaniment, age-old folk songs “The Bleating Lamb” and “Harvest Song from Thrace” evoke a world of remote mountain villages and shepherds calling across valleys. As for the soaring vocal solos, they will pierce your heart.