Modest Mussorgsky

Modest Petrovich Mussorgsky was a Russian composer, one of the group known as “The Five.” He was an innovator of Russian music in the Romantic period and strove to achieve a uniquely Russian musical identity, often in deliberate defiance of the established conventions of Western music.

Adapted from the Wikipedia article on Modest Mussorgsky.

From the period sources

Modest Mussorgsky composed the opera Khovanstchyna, which was a posthumous work. According to A Biographical Dictionary of Musicians (1900), this opera was orchestrated by Nikolas Andrejevitch Rimsky-Korsakov, alongside other posthumous operas by Dargomyzsky and Borodin.