William Pierce Butler (born October 6, 1982) is an American multi-instrumentalist and composer who is best known as a core member of the indie rock band Arcade Fire. William plays synthesizer, bass, guitar and percussion. He is known for his spontaneity and antics during performances. He is the brother of Arcade Fire frontman Win Butler. Butler received his first Academy Award nomination for his work on the original score of the film Her in 2014.