In 1995, Rolf-Dietrich Claus decided against the authenticity of BWV 565, mainly based on the stylistic characteristics of the piece. He named another problem − in its first measure the composition contains a C, a note organs in Bach's time rarely had, and which Bach almost never used in his organ compositions. In his book on BWV 565, which he expanded in 1998 to counter some of the criticisms it received, Claus also dismisses the prior version options suggested by Williams, noting that the toccata was an unknown genre for violin solo compositions of the time. Several essays in John Butt's Cambridge Companion on Bach discuss the attribution problems of BWV 565. Other biographers and scholars have left these attribution and prior version theories unmentioned, or explained the atypical characteristics of the composition by indicating it was a very early composition by Bach, probably written during his stay in Arnstadt (1703–1706).