Kuhnau's theoretical treatise "Fundamenta compositionis" survives in a single manuscript which also contains an anonymous treatise on double counterpoint ("Kurtze doch deutliche Reguln von den doppelten Contrapuncten") and two texts by Christoph Bernhard; the entire manuscript was at one point attributed to Johann Sebastian Bach. Unfortunately, "Fundamenta" appears to be a bad and partial copy from Kuhnau's original. The last five chapters are a direct copy from another Bernhard treatise on invertible counterpoint, while the discussion of modes is very similar to that in Walther's "Praecepta der musicalischen Composition" (1708), yet omits several passages included in Walther. The similarity raised an important question about Walther's well-known and highly regarded treatise: how heavily was it based upon Kuhnau's lost original? Or did both Walther and Kuhnau borrow from another writer, currently unknown?