Igor Strawinskys works stand out by virtue of their great diversity of style. There was hardly a technique or stylistic development of his time that he didn't deal with, and which did not find expression in his vast body of works, comprising virtually every musical genre. After early compositional study with Nikolai Rimsky-Korsakov, Strawinsky continued his education largely on his own. Whereas his early works, such as the wildly expressive ballets "The Firebird", "Petrushka" or "Le sacre du printemps" ("The Rite of Spring") were still created under the influence of both impressionism and Russian musical nationalism, Strawinsky developed the style of neo-classicism beginning in 1920. Harking back to old musical forms and techniques, which he then alienated and adjusted to his own clear, rhythmically pronounced style, he tended toward both timelessness as well as a positive adaptation of tradition. He once said of his music that it was "incapable of expressing anything". He regarded his composing activity as an artistic game with the widest variety of style elements. In his later works, Strawinsky also turned to the twelve-tone technique and serial composition. Besides Schönberg, Strawinsky ranks as the most influential composer of the 20th century.