William E. Caplin (born 1948) is an American music theorist who lives and works in Montreal, Quebec, Canada, where he is a James McGill Professor at the Schulich School of Music of McGill University. Caplin served as president of the Society for Music Theory from 2005 to 2007 and was its vice-president from 2001 to 2003.[1] His earlier work concentrated on the history of music theory,[2] but he is best known for a series of articles and two books on musical form in European music around 1800. The first of those books, Classical Form: A Theory of Formal Functions for the Music of Haydn, Mozart, and Beethoven[3] has been widely influential and was a major factor in the revival of interest in musical form in North-American music theory.[4]