Pitch Perfect

No musical instruments, no computers, just pure vocal magic. That's the appeal of Pentatonix, one of the world's most popular acapella groups. Since winning The SingOff talent show in 2011, the quintet has recorded albums, toured the world and won three Grammys along the way. On YouTube, they have more than 17 million subscribers and their music videos of songs like Leonard Cohen's Hallelujah and a medley of Daft Punk tracks have racked up more than 4.1 billion views. Comprised of vocalists Sco…