One of the major figures of American musical theatre, Sondheim's first success was a lyricist for others' compositions, but he wrote many Broadway scores himself. Sondheim has also written music for film.
Sondheim had a hard childhood, and he came to hate his mother, whose funeral he famously refused to attend. After his parents' divorce when he was nine, Sondheim was sent to live on a farm in Pennsylvania, where he became friend's with James Hammerstein, the father of Oscar Hammerstein II, who became something of a surrogate father, as well as a musical mentor to Sondheim.
Sondheim came out as gay in the 1980s; however, he is essentially an introverted and solitary person who has felt like an outsider since his youth. He was inducted into the Songwriters Hall of Fame in 1975.