I am a fan of barbershop choruses and quartets. Zman's best friend sings in two different choruses (Texas Millionaires and The Vocal Majority) and two quartets. He's really good. Seeing him in shows over the years has helped me appreciate this beautiful singing.
Here is Ave Maria done by the Westminster Barbershop Chorus. This chorus won the international competition in Denver this month. Their show set was fabulous (it's on YouTube, if you're interested). But this is simply gorgeous. You may have to turn your sound way up (I did) to hear it. It's worth it.