Summary from Wikipedia

Szymanowski's early works show the influence of the late Romantic German school as well as the early works of Alexander Scriabin, as exemplified by his Étude Op. 4 No. 3 and his first two symphonies. Later, he developed an impressionistic and partially atonal style, represented by such works as the Third Symphony and his Violin Concerto No. 1. His third period was influenced by the folk music of the Polish Górale people, including the ballet Harnasie, the Fourth Symphony, and his sets of Mazurkas for piano. King Roger, composed between 1918 and 1924, remains Szymanowski's most popular opera. ...