Bach wrote five series of cantatas for the Sundays and festal days of the church year—in all two hundred and ninety-five. Of these two hundred and sixty-six were written at Leipsic. They vary greatly in length, the shortest occupying twenty minutes or so in performance, the longest an hour or more. Taken together, they afford such an astonishing display of versatility that any proper characterization of them in a single chapter would be quite out of the question. A considerable number are available for study in Peters’s cheap edition, and the majority are analyzed with respect to their salient features in Spitta’s encyclopedic Bach biography. Among the great diversity of interesting qualities which they exhibit, the employment of the choral must be especially emphasized as affording the clue, already indicated, to Bach’s whole conception of the cantata as a species of religious art. The choral, especially that appointed for a particular day (Hauptlied), is often used as the guiding thread which weaves the work into the texture of the whole daily office. In such cases the chosen choral will appear in the different numbers of the work in fragments or motives, sometimes as subject for voice parts, or woven into the accompaniment as theme or in obligato fashion. It is more common for entire lines of the choral to be treated as _canti firmi_, forming the subjects on which elaborate contrapuntal choruses are constructed, following precisely the same principle of design that I have described in the case of the organ choral preludes. In multitudes of cantata movements lines or verses from two or more chorals are introduced. There are cantatas, such as “Wer nur den lieben Gott,” in which each number, whether recitative, aria, or chorus, takes its thematic material, intact or modified, from a choral. The famous “Ein’ feste Burg,” is a notable example of a cantata in which Bach adheres to a hymn-tune in every number, treating it line by line, deriving from it the pervading tone of the work is well as its constructional plan. The ways in which Bach applies the store of popular religious melody to the higher uses of art are legion. A cantata of Bach usually ends with a choral in its complete ordinary form, plainly but richly harmonized in note-for-note four-part setting as though for congregational singing. It was not the custom, however, in Bach’s day for the congregation to join in this closing choral. There are cantatas, such as the renowned “Ich hatte viel Bekümmerniss,” in which the choral melody nowhere appears. Such cantatas are rare, and the use of the choral became more prominent and systematic in Bach’s work as time went on.