It took Wagner more than 15 years to write this opera which is one reason why the music of Act Three is slightly different in style. Some ideas from the love music of Siegfried and Brünnhilde were later re-used by Wagner in a separate orchestral piece, called the "Siegfried Idyll". Many of the leitmotifs (musical ideas that belong to particular characters or ideas) are ones that were heard in the "Das Rheingold" or "Die Walküre". One unusual instrument in the orchestra is the anvil. It is played when Mime, and later Siegfried, are hammering on the anvil trying to forge the pieces of the sword together. The rhythm of this music is the same rhythm heard earlier in the Nibelung scene in "Das Rheingold".