The fugue in E flat major BWV 552/2 that ends Clavier-Übung III has become known in English-speaking countries as the "St. Anne" because of the first theme's resemblance to the St. Anne hymn 'O God, Our Help in Ages Past', a hymn that would have been unknown to Bach. A fugue in three sections of 36 bars, 45 bars and 36 bars, with each section a separate fugue on a different theme, it has been called a triple fugue, although only the first theme is combined with the second and third themes; for that reason the second and third sections are sometimes referred to as double fugues. The number three is pervasive and has been understood to represent the Trinity. The description of Albert Schweitzer (see below) follows the 19th-century tradition of associating the three sections with the three different parts of the Trinity. The number three, however, occurs many other times: in the number of flats of the key signature; in the number of sections; and in the number of bars in each section, each a multiple of 3 x 3. Each of the three themes of the fugues seems to grow from the previous ones. Indeed, Hermann Keller has suggested that the second theme 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 theme to crotchet figures in the countersubject to the first theme. The 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.
"The triple fugue ... is a symbol of the Trinity. The same theme recurs in three connected fugues, but each time with another personality. The first fugue is calm and majestic, with an absolutely uniform movement throughout; in the second the theme seems to be disguised, and is only occasionally recognisable in its true shape, as if to suggest the divine assumption of an earthly form; in the third, it is transformed into rushing semiquavers as if the Pentacostal wind were coming roaring from heaven."
-- Albert Schweitzer, Jean-Sebastien Bach, le musicien-poete, 1905