Stephen Sondheim Composer and lyricist Stephen Sondheim. He was mentored by Oscar Hammerstein, and went on to revolutionize musical theatre. His first major success was writing lyrics for West Side Story. Sondheim wrote the lyrics for Gypsy. He composed the music and wrote the lyrics for A Funny Thing Happened on the Way to the Forum, Follies, A Little Night Music, Sweeny Todd, Sunday in the park with George, and Into the Woods. In 1954 he wrote the musical Saturday Night but it wasn't performed for 40 years. There's a new cast recording of it.