During the Romantic Era, composers experimented with new forms of musical expression through variations in composition length, harmonies, and tonal relationships. The piano was used to convey emotion through melodic, harmonic, and rhythmic qualities. Art songs set poetry to music to further enhance poems, and could be strophic or through-composed. Romantic opera focused on nationalism and folk themes, with Mozart's Die Zauberflöte as a famous example. Franz Schubert was a famous composer during this period known for his Lieder, who died in 1828 in Vienna at a young age. Giuseppe Verdi and Richard Wagner were other influential Romantic opera composers.