Italian cellist, librettist and composer. Haym was born of German parents in Italy, where he must have received a sound musical training. He played under Corelli in Cardinal Ottoboni's orchestra in Rome from 1694 through 1700, also composing vocal music at the time. He served the second Duke of Bedford in London from 1701 through 1711, and later the Duke of Chandos. Together with Charles Dieupart and Thomas Clayton, he was an important figure in London's Italian opera. He played the cello for Clayton's Arsinoe (1706). the first full-length Italian-style opera to be staged in England. Later he wrote substituion arias for Bononcini's Camilla (1706) and Etearco (1708), as well as Scarlatti's Pirro e demetrio (1708) and various pasticcios. The great success of Handel's Rinaldo at the Haymarket greatly hurt the Clayton/Dieupart/Haym venture at the Drury Lane Theatre, and at first Haym joined the detractors who decried the "new style" of Handel's operas, but he shrewdly evaluated the newcomer's talents and probable future; instead of sulking and opposing him like Pepusch and others, he soon formed an association with him that lasted over fifteen years. He adapted many libretti for Handel , including Radamisto (1720), Giulio Cesare (1724), Tamerlano (1724), and Rodelinda (1725). Haym performed chamber music, was active as a teacher, edirted Italian literature, and produced catalogs of Greek and roman coins and rare Italian books. His works include sacred and secular vocal music as well as sonatas. Hawkins considered him a great composer, though the composer has been consistently obscured by the librettist. Haym had himself planned the writing of a history of music on a grand scale.