Lied is a term to describe setting poetry to classical music to create a piece of polyphonic music. The term is used for songs from the late fourteenth or early fifteenth centuries or even to refer to Minnesang from as early as the 12th and 13th centuries. It later came especially to refer to settings of Romantic poetry during the late eighteenth and nineteenth centuries, and into the early twentieth century. Examples include settings by Joseph Haydn, Wolfgang Amadeus Mozart, Ludwig van Beethoven, Franz Schubert, Robert Schumann, Johannes Brahms, Hugo Wolf, Gustav Mahler or Richard Strauss. Among English speakers, however, "lied" is often used interchangeably with "art song" to encompass works that the tradition has inspired in other languages. The poems that have been made into lieder often center on pastoral themes or themes of romantic love.