Peter Hollens is an American pop singer and producer best known for his work on YouTube as an a cappella cover artist. With over 1.5 Million subscribers. Hollens has collaborated with some of his favorite artist, including Brian Wilson, Jason Mraz, Hunter Hayes, Lindsey Stirling, George Watsky & The Piano Guys. He has released over 125+ digital singles. He has been described as the one man Pentatonix, and was in five episodes of NBC's The Sing Off.