Complex sentence: Ravel and Debussy were at work developing and performing their Impressionistic forms; and in 1911 the premiere of Richard Strauss's opera "Der Rosenkavalier" further pushed music toward a new style.
Split into simpler sentences: Ravel and Debussy were at work developing and performing their Impressionistic forms. And in 1911 the premiere of Richard Strauss's opera "Der Rosenkavalier" further pushed music toward a new style.