Answer
Boleslav Yavorsky, a Russian composer and music theorist, gave Mykola Leontovych private lessons. Yavorsky taught Leontovych music theory and composition, and he also introduced him to the music of other Russian composers, such as Modest Mussorgsky and Nikolai Rimsky-Korsakov. Leontovych's time with Yavorsky was formative, and it helped to shape his own musical style.