In 1794 at the Haymarket Theatre he produced Auld Robin Gray, a musical play in two acts; and this was followed by other works of the same class: Who Pays the Reckoning?
Up All Night, or The Smuggler's Cave, Britain's Jubilee, The Maniac, or Swiss Banditti, and Plots, or The North Tower are the titles of musical plays by Arnold presented by the Drury Lane Company during their occupancy of the English Opera House.
The theatre was afterwards open under his own management, when his operas The King's Proxy, The Devil's Bridge, The Americans, Frederick the Great, Baron Trenck, Broken Promises and dramas including Two Words and Free and Easy were produced in succession.
William Hazlitt wrote in 1816 of Arnold's The King's Proxy that it was "the essence of four hundred rejected pieces … with all that is threadbare in plot, lifeless in wit, and sickly in sentiment" and that "Mr. Arnold writes with the fewest ideas possible; his meaning is more nicely balanced between sense and nonsense than that of any of his competitors; he succeeds from the perfect insignificance of his pretensions, and fails to offend through downright imbecility."
In 1812 Arnold had been invited to undertake the direction of the Drury Lane Theatre; he resigned his office on the suicide of Samuel Whitbread in 1815.
In 1824 Arnold produced for the first time in England a version of Carl Maria von Weber's Der Freischütz, which had been previously refused by the two patent theatres.
The English operas Nourjahad by Edward Loder and The Mountain Sylph by John Barnett were produced under Arnold's management.