He was born in West Chester, Pennsylvania and began to compose at the age of seven. He later developed a good baritone voice, and for a while considered becoming a professional singer. He even made a few recordings, including his own Dover Beach. He studied at the Curtis Institute of Music in Philadelphia before becoming a fellow of the American Academy in Rome in 1935. The following year he wrote his String Quartet in B major, the second movement of which he would arrange for string orchestra as his Adagio for Strings. This piece has remained popular to this day, being used in the films Platoon and The Elephant Man and recently being given an electronic treatment by William Orbit (a remix by Ferry Corsten sold well in both the US and the UK).
The popularity of the Adagio has somewhat overshadowed the rest of Barber's output. However, he is seen as one of the most talented American composers of the 20th century. He did not go in for the sort of extreme experimentalism of some other American composers of his generation but stuck to relatively traditional harmonies and forms. His work is lushly melodic and has often been described as neo-romantic. None of his works come close to the popularity of the Adagio, but several of them are often performed and recorded.
His various songs for voice and piano are some of the most popular 20th century songs in the classical repertoire. They include a setting of Matthew Arnold's "Dover Beach," originally written for string quartet and baritone, and the Hermit Songs on anonymous Irish texts of the 8th to 13th centuries. Barber also wrote a Piano Sonata (1949) which is frequently heard. The piece was commissioned by Richard Rodgers and Irving Berlin and was first performed by Vladimir Horowitz. It was the first large scale American piano work to be premiered by such an internationally renowned pianist.
Barber also completed several operas, Vanessa (1952-57) being the best known. Barber worked on it very rapidly, and the work would have likely been completed much earlier but for his librettist and partner Gian Carlo Menotti's reluctance to finish the libretto. When the work was premiered at the Metropolitan Opera in New York City, it was a critical and popular success and Barber won a Pulitzer prize for it. At the European premiere it met with a chillier reception, however, and is now little played there, although it remains popular in America.
Although never a prolific composer, Barber wrote much less after the flop of his opera Antony and Cleopatra (with a libretto by the film director Franco Zeffirelli) in 1966. He died in New York City in 1981.