The Pirates of Penzance, or The Slave of Duty, is a comic opera in two acts, with music by Arthur Sullivan and libretto by W. S. Gilbert. It remains popular today, taking its place along with The Mikado and H.M.S. Pinafore as one of the most frequently played Gilbert and Sullivan operas. Its 1981 Broadway revival by Joseph Papp ran for 787 performances and spawned many imitations. The Pirates of Penzance was the only Gilbert and Sullivan opera to have its official premiere in New York. At the time, American law offered no copyright protection to foreigners. After their previous opera, H.M.S. Pinafore, was a hit in London, over a hundred American companies quickly mounted unauthorized "pirated" productions, often taking considerable liberties with the text and paying no royalties to the creators. By mounting their next opera in New York, Gilbert and Sullivan hoped to forestall further "piracy" by establishing the official production in America before others could copy it. This proved successful in allowing them to get some of the profits; however, it failed to ever establish any actual copyright, and future operas would return to premièring in London. The creative period for Pirates was unusual, in that Sullivan composed the acts in reverse — bringing the completed Act II with him, with Act I existing only in sketches. When he arrived in New York, he found that he had left the sketches behind, and he had to reconstruct the first act from memory.