The conception and composition of this ''Bühnenfestpiel'' ("stage festival play") spanned close to 30 years, and was based on German and Old Norse mythology as well as historical subjects. It requires four separate evenings, and at least 15 hours to perform.<ref>Millington, Barry. "Der Ring des Nibelungen," in ''New Grove Dictionary of Opera'', 1994.</ref> The following four music dramas make up the ''Ring'' cycle: | The conception and composition of this ''Bühnenfestpiel'' ("stage festival play") spanned close to 30 years, and was based on German and Old Norse mythology as well as historical subjects. It requires four separate evenings, and at least 15 hours to perform.<ref>Millington, Barry. "Der Ring des Nibelungen," in ''New Grove Dictionary of Opera'', 1994.</ref> The following four music dramas make up the ''Ring'' cycle: |