Hector Berlioz was a French Romantic composer, best known for his compositions Symphonie fantastique, Grande messe des morts (Requiem), Les Troyens, and La damnation de Faust.
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 several concerts with more than 1,000 musicians.
He also composed around 50 compositions for voice, accompanied by piano or orchestra. His influence was critical for the further development of Romanticism, especially in composers like Richard Wagner, Nikolai Rimsky-Korsakov, Franz Liszt, Richard Strauss, and Gustav Mahler.