His compositional style had already begun changing before the October Revolution deprived him of his homeland. The harmonic writing in "The Bells" was composed in 1913 but not published until 1920. This may have been due to Rachmaninoff's main publisher, Gutheil, having died in 1914 and Gutheil's catalog being acquired by Serge Koussevitsky. It became as advanced as in any of the works Rachmaninoff would write in Russia, partly because the melodic material has a harmonic aspect which arises from its chromatic ornamentation. Further changes are apparent in the revised First Piano Concerto, which he finished just before leaving Russia, as well as in the Op. 38 songs and Op. 39 Études-Tableaux. In both these sets Rachmaninoff was less concerned with pure melody than with coloring. His near-Impressionist style perfectly matched the texts by symbolist poets. The Op. 39 Études-Tableaux are among the most demanding pieces he wrote for any medium, both technically and in the sense that the player must see beyond any technical challenges to a considerable array of emotions, then unify all these aspects.