The art song and the opera are two very different genres of music. Franz Schubert wrote the art song The Erlking in 1815. Giacomo Puccini wrote his opera, La Boheme, in 1896. Richard Wagner wrote the opera The Valkyrie in 1856. Schubert is known best for his art songs, which are over 600 in number. Puccini and Wagner are known for their operas. These genres have several important differences.
The singing in these pieces is quite different. The Erlking involves just a soloist acting in several functions; a man, his son, a narrator, and the Erlking. The vocalist sings each role with a different inflection. In La Boheme and The Valkyrie, the pieces require multiple characters. These characters have individual arias and recitatives and dialogue between them. In addition to that, the operatic singing is more characterized, and has the potential to be more dramatic than art song.
The stage setup for these pieces would be fairly contrasting. An art song (The Erlking) has a closer setup to that of a solo recital. The opera (such as La Boheme) is a very elaborate production. It contains many different sets and uses lighting as well. The characters wear costumes and makeup to add more effect. Opera is closer to a combination of all art than the art song, which is simply music.
Art song and opera use completely different instrumentation. Art songs, like The Erlking, typically have only piano accompaniment. Opera is quite the opposite. Wagner’s operas, like The Valkyrie, require massive orchestras.
Another thing to look at is the different styling of operas. Wagner and Puccini have quite different compositional techniques. The lines Puccini uses are intensely emotional, yet short. His orchestrations have the orchestra strengthening the melodic line. Wagner’s approach was to put the audience in a state of awe. His characters were often gods or other mythological beings. He used short themes for each of his characters. The chromatic and dissonant...