TETRALOGY • DICCIONARIO INGLES.COM • Definition of Tetralogy

... theatre or concert attended each of the four performances in one week, and are supposed to have gone mad. With the women I have made a great hit. The pianoforte scores sell by the half-dozen. I am now in the country, and feel tolerably cheerful. My work also pleases me again; my Nibelung tetralogy is completely designed, and in a few months the verse also will be finished. After that I shall be wholly and entirely a "music-maker," for this work will be my last poem, and a litterateur I hope I shall never be again. Then I shall have ...

— Correspondence of Wagner and Liszt, Volume 1 • Francis Hueffer (translator)