Assess the Following as Probably True,as Probably False,as Requiring Further

Assess the following as probably true,as probably false,as requiring further documentation before judgment,or as a claim that cannot properly be evaluated.Consider both the nature of the claim and the source.
According to a Baron Gottfried von Swieten,King Frederick of Prussia claimed that he had once given a chromatic theme to Johann Sebastian Bach,who had immediately made of it a fugue in four parts,then in five parts,and finally in eight parts.
-From H.T.David and A.Mendel,The Bach Reader,reported in Gödel,Escher,Bach,by Douglas R.Hofstadter
Probably false.One needs to know something of music to realize how incredible this remark is.To improvise a six-part fugue is nearly beyond imagination (Hofstadter likens it to playing sixty games of chess simultaneously while blindfolded and winning them all).Even Bach,whose genius strains credibility on many counts,is unlikely to have been able to improvise an eight-part fugue.Presumably either King Frederick or the good Baron was doing some exaggerating.