During the course of his first ten years as cantor in Leipzig (1723 - 1733), Bach built up a formidable stock of cantatas for weekly use in the Thomaskirche and Nicolaikirche. Few subsequent additions appeared during the 1730s and 1740s, but there are a few parody works. Among them is BWV 191, unique among Bach's sacred cantatas in being the only one not to use the vernacular. First performed on Christmas Day 1745, it is an adaptation of three sections of the Gloria from the Mass in B minor, BWV 232. The first is the opening chorus of the Mass' Gloria, both text and scoring virtually unchanged except for the omission of the bassoons in the cantata. The other two movements are marked post orationem (after the sermon). The duet for soprano and tenor is an abridged version of "Domine Deus" (No. VII in the Mass) with the text changed to the first part of the doxology, "Gloria Patri," while the final choral section completes the text of the doxology to the music used in the Mass for the "Cum Sancto Spiritu" (No. XI), the music slightly altered to accommodate the text. The work is in fact an interesting example of the manner in which Bach constantly refined and rethought existing material, a midpoint between the original conception of the Gloria, which dates from 1733, and its final form as part of the towering complete Mass of 1748. ~ Brian Robins, All Music Guide
