[1] Horn made his singing debut on 26 June 1809 with a performance in the comic opera Up All Night, or the Smuggler's Cave (words by Samuel James Arnold and music by Matthew Peter King) at Lyceum Theatre, London.

He achieved prominence with his portrayal of Caspar in the English version of Carl Maria von Weber's Der Freischütz in 1824.

[1] He soon became a prolific composer for the stage; many of his songs for larger dramatic works became popular, including "On the banks of Allan Water" from Rich and Poor (1812), "I know a bank" from The Merry Wives of Windsor (1823), "The deep, deep sea" in Honest Frauds (1830), and "Cherry Ripe" from Paul Pry (1826).

In addition to giving singing performances, he staged works by Storace, Weber, Wolfgang Amadeus Mozart, and Gioachino Rossini.

He briefly returned to London for a few years, overseeing the debut of his Honest Frauds (1830) and serving as music director of the Olympic Theatre from 1831 to 1832, before sailing back to New York.