Educated at Chapel Royal, Arnold became composer to Covent Garden Theatre; his first annual production was The Maid of the Mill (1765). Subsequent positions were as music director of the Theatre Royal in the Haymarket (1777), organist and composer to the Chapel Royal (1783), conductor of the Academy of Ancient Music (1789), and organist at Westminster Abbey (1793). His compositions include sonatas, symphonies, and oratorios, as well as ballad operas, farces, and pantomimes. His Cathedral Music (1790), a collection of service music, was an important supplement to William Boyce's Cathedral Music.