previous ones. Indeed, musicologist Hermann Keller has suggested that the second subject is "contained" in the first. Although perhaps hidden in the score, this is more apparent to the listener, both in their shape and in the resemblance of the quaver second subject to crotchet figures in the countersubject to the first subject. Similarly, the semiquaver figures in the third subject can be traced back to the second subject and the countersubject of the first section.Form of the fugueThe form of the fugue conforms to that of a 17th-century tripartite ricercar or canzona, such as those of Froberger and Frescobaldi: firstly in the way that themes become progressively faster in successive sections; and secondly in the way one theme transforms into the next. Bach can also be seen as continuing a Leipzig tradition for contrapuntal compositions in sections going back to the keyboard ricercars and fantasias of Nicolaus Adam Strungk and Friedrich Wilhelm Zachow. The tempo transitions between different sections are natural: the minims of the first and second sections correspond to the dotted crotchets of the third.Source of the subjectsMany commentators have remarked on similarities between the first subject and fugal themes by other composers. As an example of stile antico, it is more probably a generic theme, typical of the fuga grave subjects of the time: a "quiet " time signature, rising fourths and a narrow melodic range. As points out, the similarity to the subject of a fugue by Conrad Friedrich Hurlebusch, which Bach himself published in 1734, might have been a deliberate attempt by Bach to blind his public with science. Roger Wibberly has shown that the foundation of all three fugue subjects, as well as of certain passages in the Prelude, may be found in the first four phrases of the chorale "O Herzensangst, O Bangigkeit". The first two sections of BWV 552/2 share many affinities with the fugue in E major BWV 876/2 in The Well-Tempered Clavier, Book 2, written during the same period. Unlike true triple fugues, like the F minor BWV 883 from the same book or some of the contrapuncti in The Art of the Fugue, Bach's intent with BWV 552/2 may not have been to combine all three subjects, although this would theoretically have been possible. Rather, as the work progresses, the first subject is heard singing out through the others: sometimes hidden; sometimes, as in the second section, quietly