In his 1851 essay "Opera and Drama", Wagner had set out new principles as to how music dramas should be constructed, under which the conventional forms of opera (arias, ensembles, choruses) were rejected. Rather than providing word-settings, the music would interpret the text emotionally, reflecting the feelings and moods behind the work, by using a system of recurring leitmotifs to represent people, ideas and situations. "Das Rheingold" was Wagner's first work that adopted these principles, and his most rigid adherence to them, despite a few deviations – the Rhinemaidens frequently sing in ensemble.