"Angels and Saints at Epheseus" has topped Billboard's classical charts for weeks.
The album was recorded by the Benedictines of Mary, Queen of Apostles at their priory in rural Missouri.
The prioress and music arranger for the Sisters of Mary, Queen of the Apostles is Mother Cecilia.
She says the high quality of the nuns' music comes from singing together eight times a day, which they do to express their love for God.
"The fact that we are singing together so often throughout the day, our voices, our whole heart kind of becomes one in the heart of God," said Mother Cecilia. "We're not just some choir that comes together for practice every Tuesday night."
The success of the album is unimportant to the nuns.
"These CDs are absolutely non-essential to our life, our life of prayer," she said. "If we hadn't recorded, or if we don't record again, it really wouldn't have any bearing, any effect on our life."
Hear two tracks from the album:
- Mother Cecilia, prioress and music arranger for the Sisters of Mary, Queen of the Apostles, whose latest album is "Angels and Saints at Epheseus."
This segment aired on July 1, 2013.