(b Berlin, 13 Feb 1840; d London, 13 Sept 1906). German violinist, conductor and composer. He first studied the violin at the age of six in Berlin with Eduard and Leopold Ganz, moving to Brussels in 1849 to study with Bériot. At the onset of Bériot's blindness he went to Paris, where, on Halévy's recommendation, he joined Massart's class at the Conservatoire (1852); he also studied composition with Réber, Gevaert and Chéri. After winning the premier prix for violin in 1861 he played for two years at the Opéra-Comique, and then won the competitive post of first violin at the Opéra, where he played in many notable productions, including Tannhäuser. He also formed a string orchestra of 16 players which gave a successful series of concerts at the Société Nationale des Beaux-Arts.
From 1868 to 1870 Jacobi was conductor at the Bouffes-Parisiens, where he directed many Offenbach performances as well as composing some operettas (according to Fétis, two or three ‘without value or consequence’). On the outbreak of the Franco-Prussian War he moved to London to conduct at the Alhambra Theatre for the 1871–2 season; he remained for 26 years, composing 103 ballets and divertissements, which were also widely performed abroad. His comic operas include The Black Crook (which ran for 310 performances) and La mariée depuis midi; he also wrote incidental music for Henry Irving's productions at the Lyceum. In 1898 he transferred to the Crystal Palace, for which he wrote two ballets, and was briefly conductor at the London Hippodrome. He taught at the Royal College of Music from 1896. His concert works include two violin concertos, a viola concerto, violin pieces and songs.