After 1735 the chronology of the Cantatas is not certainly ascertained. Of those that fall after the Ziegler year, as we may term it, the majority can only be dated approximately as circa 1740, that is, anywhere between 1735 and 1744. Nor, except rarely, can we detect in their libretti the work of those on whom Bach elsewhere relied. Weiss, who died late in 1737, is only an occasional contributor. The texts of this period, in fact, are the outcome of Bach’s own experiments in libretto form. Thirty-three of them are Choral Cantatas, whose evolution it remains to trace concisely. That Bach should have turned to Lutheran hymnody, chiefly of the fifteenth and sixteenth centuries, and that the Cantatas built upon it should be his most perfect religious work is not surprising. The hymns and their melodies were the foundations upon which the temple of German Protestantism had been reared. They appealed vividly and powerfully to Bach’s spiritual nature, and profoundly influenced his musical utterance. His whole career, as Sir Hubert Parry points out,(453) was an effort to widen his means for self-expression. And the Choral Cantata, in effect, was the reconciliation or blending of this self-discipline. It was the supreme achievement of Bach’s genius to assert the faith and idealism of Lutheran hymnody with the fullest resources of his technique. It is not our task to consider the hymn libretto in its relation to the structure of Bach’s latest Cantatas. Necessarily it tied him to a stereotyped design, which he clung to with greater persistency because it exactly fulfilled his devotional purpose. But experience compelled him, after a brief trial, to discard the simple hymn libretto. In the earlier Leipzig years as many as eight Choral Cantatas(454) are set to the unaltered text of a congregational hymn. In the later Leipzig period only two(455) libretti are of that character. Bach, in fact, soon realised that, while the unaltered hymn-stanza, with its uniform metre and balanced rhyme, was appropriate to the simple Choral or elaborate Fantasia, it was unmalleable for use as an Aria or Recitative. Hence, retaining the unaltered Hymn-stanza for the musical movements congruous to it, he was led to paraphrase, in free madrigal form, those stanzas which he selected for the Arias and Recitativi.