When a cappella-centric rom-com Pitch Perfect hit the big screen, it gifted the world with a newfound appreciation for acoustic pipes. And if we had to narrow down one of the best a cappella groups out there, it'd be the Pentatonix. This five person crew has amassed 1.4 billion views on YouTube, taken home a Grammy and hit the top of Billboard's charts. Catch them on tour with guests Us The Duo.