http://www.youtube.com/watch?v=4t3Vmo_EM8YTom Lehrer quotes Haydn on the piano (not in his singing) in his brilliant satire "Wernher von Braun":
http://www.youtube.com/watch?v=QEJ9HrZq7Rofrom which I lifted part of my sig line.
But be sure always to call it please an allusion, not plagiarism.
Tom Lehrer also wrote a song about plagiarism, but I digress from my earlier digression.
To get back on topic, here is an excerpt from Wikipedia:
"The Deutschlandlied ('Song of Germany') ... has been used wholly or partially as the national anthem of Germany since 1922. The music was written by Joseph Haydn in 1797 as an anthem for the birthday of the Austrian Emperor Francis II of the Holy Roman Empire. In 1841, the German linguist and poet August Heinrich Hoffmann von Fallersleben wrote the lyrics of "Das Lied der Deutschen" to Haydn's melody, lyrics that were considered revolutionary at the time.
"The song is as well-known by the opening words and refrain of the first stanza, 'Deutschland, Deutschland über alles' (literally, 'Germany, Germany above all'), but this has never been its title. The line 'Germany, Germany above all' meant that the most important goal of the Vormärz revolutionaries should be a unified Germany overcoming the perceived anti-liberal Kleinstaaterei. Alongside the Flag of Germany it was one of the symbols of the March Revolution of 1848.
"In order to endorse its republican and liberal tradition, the song was chosen for national anthem of Germany in 1922, during the Weimar Republic. West Germany adopted the Deutschlandlied as its official national anthem in 1952 for similar reasons, with only the third stanza sung on official occasions. Upon German reunification in 1990, only the third stanza was confirmed as the national anthem."
Read more (including the lyrics):
http://en.wikipedia.org/wiki/Deutschland_Über_Alles