Louis-Hector Berlioz (1803–69) was a French Romantic composer, best known for his Symphonie fantastique and Grande messe des morts (Requiem). Berlioz made significant contributions to the modern orchestra with his Treatise on Instrumentation. He specified huge orchestral forces for some of his works, and conducted concerts with more than 1,000 musicians. His influence was critical for the further development of Romanticism, especially for composers such as Richard Wagner, Nikolai Rimsky-Korsakov, Franz Liszt, Richard Strauss and Gustav Mahler.
The Belgian composer César Franck once said that Berlioz’s whole output is made up of masterpieces. Each of the composer’s dozen great works was the realization of a distinct conception, rather than successive efforts to attain perfection. Unlike many composers, Berlioz almost never repeated himself. Rather, he created a fresh style for each of his subjects, with the result that familiarity with one is no guarantee of ready access to another.