Is there some kind of weird vocal vortex in Minnesota? The state turns out so many excellent choral groups — at the school, church and professional levels — that it can arguably be dubbed the choral center of the U.S. The members of the male vocal ensemble called Cantus, who huddled around Bob Boilen's desk to sing for us, hail from that vortex — specifically Minneapolis-St. Paul. A quick note on the group's name, because it's more appropriate than you might think. "Cantus" means "singing" in Latin, but it also refers to an old European tradition. A student group who gathered to sing traditional songs and drink beer was once called a "cantus." And this modern-day group of Minnesotans indeed got its start in 1995 as a student singing group at St. Olaf College in Northfield, Minn. They didn't tell us much about the beer, though. Cantus went professional in 2000 and has cut 15 albums on its own label. Unlike some choral groups who specialize in one style of music, Cantus prides itself on diversity. Just take a look at the three songs its members chose for this concert. "Wanting Memories" is a song steeped in African-American culture, written by Ysaye Barnwell from Sweet Honey in the Rock. "Zikr," composed by A.R. Rahman — the same guy who scored the hit movie Slumdog Millionaire — has roots in the Sufi tradition, where deep chords and repeated phrases signal a slow burn toward religious ecstasy. And the group closes with German composer Franz Biebl's gorgeous "Ave Maria," a signature piece for the group that blends traditional plainsong (or chant) with delicate melody and voluptuous harmonies that ascend heavenward. Listening to Cantus, you understand that there's something about a group of people singing that touches listeners on a very human level. Perhaps it explains why so many of us sing — and not just in the shower. Chorus America estimates that 42.6 million American adults and children sing in choirs. (A lot of them live in Minnesota!) For the rest of us, whose pipes aren't quite that golden? We've always got excellent groups like Cantus to do the singing for us.