jtkennedy@asu.edu Event Image:  Pentatonix is an a cappella group of five vocalists, Scott Hoying, Kirstie Maldonado, Mitch Grassi, Avi Kaplan and Kevin Olusola, originating from Arlington , Texas . The group won the third season of The Sing-Off on November 28, 2011 broadcast on NBC , singing an a cappella arrangement