Son of Thomas Arnold and Princess Amalia, Samuel had a prolific career as composer, organist, and scholar. He began as choir boy at the Chapel Royal, and by his twenties was writing successful operas such as The Maid of the Mill (1765), and playing the harpsichord at Covent Garden in London. At age 29, he and Thomas Pinto became owners of Maryleburn Gardens, which later failed after someone embezzled a great deal of money; Arnold lost £10,000 on the venture.

Oxford awarded Arnold a Doctor of Music degree in 1773, and his works were performed in London theaters throughout that decade. In 1783 he became organist at the Chapel Royal, in 1789 director of the Academy of Ancient Music, and in 1793 organist at Westminster Abbey. His works include:

• The Psalms of David, 1791 (co-authored with John W. Callcott)