I thank you, Capt Lightening, for posted this great word.
They vary widely in character, from extremely simple settings of a "cantus firmus", to contrapuntal tours-de-force such as elaborate canons and quodlibets.
Quodlibet is one archaic term that I have never used in Scrabble - and often, my custom Scrabble game accuses me of being archaic!
From Wikipedia: A quodlibet (/ˈkwɒdlɪbɛt/; Latin for "whatever you wish" from quod, "what" and libet, "pleases") is a musical composition that combines several different melodies—usually popular tunes—in counterpoint, and often in a light-hearted, humorous manner.