A five-person a cappella group based out of Arlington, Texas, Pentatonix are best known for winning the third season of NBC's The Sing-Off in 2011. Formed by high-school friends Kirstie Maldonado, Mitch Grassi, and Scott Hoying, the group got its initial start after its version of Beyoncé and Lady Gaga's "Telephone," recorded for a local Glee-related contest, started garnering attention on YouTube. The band then added members Avi Kaplan and Kevin Olusola, renamed itself Pentatonix, and auditioned...