Because of the first theme’s similarities to the hymn “O God, Our Help in Ages Past,” Bach’s Fugue in E-flat Major (BWV 552/2) is known in the English-speaking world as St. Anne’s Fugue, even though this hymn would not have been known to composer.
The contrapuntal form typifies fugue construction, where different melody lines are played against each other. In this case, Bach writes for five voices.
St. Anne’s Fugue is a triple fugue, and Christians have long drawn parallels between this fugue and the Trinity. The number three is pervasive. There are three flats. The number of measures in each part is a multiple of three: 36, 45, and 36. Each successive part seems to grow while incorporating the previous theme.