Pentatonix are an American a cappella group from Arlington, Texas, consisting of vocalists Scott Hoying, Mitch Grassi, Kirstin Maldonado, Matt Sallee, and Kevin Olusola. Characterized by their pop-style arrangements with vocal harmonies, basslines, riffing, percussion, and beatboxing, they produce cover versions of modern pop works or Christmas songs, sometimes in the form of medleys, along with original material. Pentatonix was formed in 2011 and subsequently won the third season of NBC's The Sing-Off, receiving $200,000 and a recording contract with Sony Music. When Sony's Epic Records dropped the group after The Sing-Off, the group formed its YouTube channel, distributing its music through Madison Gate Records, a label owned by Sony Pictures.

Music performed a cappella, less commonly spelled a capella in English, is music performed by a singer or a singing group without instrumental accompaniment. The term a cappella was originally intended to differentiate between Renaissance polyphony and Baroque concertato musical styles. In the 19th century, a renewed interest in Renaissance polyphony, coupled with an ignorance of the fact that vocal parts were often doubled by instrumentalists, led to the term coming to mean unaccompanied vocal music. The term is also used, rarely, as a synonym for alla breve.