The Artful Codger's got that right. They met at a small religious college in the South so they are rooted in black gospel music but, it seems to me, their influences are The Swingle Singers, The Four Freshmen and The Hi-Lo's (Listen to the Clark Burroughs-like falsetto
rides). I, too, was disappointed when they started using some instrumental accompaniment and branching into a more secular repitore. If there was, ever, a group that didn't need backup, it was Take6.
Their audience was, primarily, black. It took the rest of us a while to catch up.