O ewiges Feuer, o Ursprung der Liebe, BWV 34a
History and text. The cantata was composed in Leipzig most likely in 1725 or 1726, or 1727 or later, as a wedding commission, and performed shortly after its composition. As the choral numbers are lost, it is unknown whether any chorale theme had been used by Bach as inspiration for the writing. The libretto, by an unknown author, is partly based on scripture. Specifically, movements 3 and 4 set verses from Psalm 128 (), whereas the text of the final chorale is drawn from the biblical Book of Numbers (). Scoring and structure . The piece is scored for four vocal soloists (soprano, alto, tenor, bass) and four-part choir, two oboes, two flauti traversi, timpani ("tamburi"), three trumpets ("trombe") in D, two violins, viola, and basso continuo. The cantata has seven movements, divided in two parts (four movements performed before the sermon, and the remaining three afterwards): Music. The opening chorus draws on imagery of eternal fire, represented in the strings. This is followed by a short secco bass recitative ending on an imperfect B minor cadence. The third movement exists only in reconstructed forms; it likely opened with strings and continuo. Its  structure oddly alternates between aria and recitative episodes. The chorus appeals for peace. The second part opens with an alto aria that also appears in BWV 34.1. It includes an accompaniment of flute and muted violin in octaves. A brief secco soprano recitative leads into the closing chorus for which only soprano and bass parts are extant. As a result, it is unclear what role the other voices would play in the movement.