Complex sentence: He became part of the Parisian literary circle of the symbolist poet Mallarmé, and an admirer of Wagner, then went on to experiment with impressionism in music, atonal music and chromaticism.
Split into simpler sentences: He became part of the Parisian literary circle of the symbolist poet Mallarme. At first an admirer of Richard Wagner, he went on to experiment with impressionism in music, atonal music and chromaticism.