Most people know Mitch Grassi from Pentatonix, who won NBC’s talent show The Sing-Off in 2011, parlayed that opportunity into YouTube stardom, and eventually won three Grammys and made history...
Read MoreA cappella sensations Pentatonix have reached superstar status — with three Grammys, 13 million YouTube subscribers, their own Christmas special, and several platinum records to their credit — but at...
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