Pentatonix

Pentatonix is a quintet from Arlington, Texas, performing "a cappella". Winners of season 3 of NBC's talent show "The Sing-Off", they are named after the world's most widely recognized five-note musical scale.
Pentatonix is comprised of lead vocalists Scott Hoying (22), Kirstie Maldonado (21) and Mitch Grassi (21), vocal bass Avi Kaplan (24) and beatboxer Kevin “K.O.” Olusola (25) and, while the individuals would maintain that each of their fellow band members is irreplaceable, the fact remains that 24-hours before their audition for The Sing-Off they still hadn’t all officially met.