Johann Sebastian Bach composed the church cantata (God the Lord is sun and shield), 79, in Leipzig in 1725, his third year as Thomaskantor, for Reformation Day and led the first performance on 31 October 1725.
The text was written by an unknown poet, who did not refer to the prescribed readings for the day. Bach began the libretto for the feast with a quotation from Psalm 84 and included two hymn stanzas, the first from Martin Rinckart's "", associated with Reformation Day in Leipzig, as the third movement, and as the last movement the final stanza of Ludwig Helmbold's "". Bach composed a work of "festive magnificence", structured in six movements, with an aria following the opening chorus, a pair of recitative and duet following the first chorale. He scored the work for three vocal soloists, a four-part choir, and a Baroque instrumental ensemble of two horns, timpani, two transverse flutes (added for a later performance), two oboes, strings and continuo. He achieved a unity within the structure by using the horns not only in the opening but also as obbligato instruments in the two chorales, the first time even playing the same motifs.
Bach performed the cantata again, probably in 1730. He later reworked the music of the opening chorus and a duet again in his Missa in G major, BWV 236, and the music of an alto aria in his Missa in A major, BWV 234.
History and words
Bach composed the cantata in his third year as Thomaskantor in Leipzig. While he had written complete annual cycles for many occasions of the liturgical year the first two years in the position, he slowed down in the third. For the Reformation Day, he composed this new cantata, his first extant work for the occasion. The prescribed readings for the feast day were from the Second Epistle to the Thessalonians, "be steadfast against adversaries" (), and from the Book of Revelation, fear God and honour him (). The writer of the text – an unknown poet – was not concerned about the readings, and began with a quotation from Psalm 84 (). He included the first stanza from Martin Rinckart's hymn "" and as the closing chorale the final stanza of Ludwig Helmbold's hymn "". According to the Bach scholar Klaus Hofmann, the first of these hymns was sung regularly after the sermon on Reformation Day in Leipzig.
Bach first performed the cantata on 31 October 1725. He repeated it again, probably in 1730, with minor changes in the scoring, doubling the oboes by flutes and assigning a flute as the obbligato instrument in the alto aria. He used the music of the opening chorus and the duet again in his Missa in G major, BWV 236, and the music of the alto aria in his Missa in A major, BWV 234.
Music
Structure and scoring
Bach structured the cantata in six movements. A choral movement is followed by an aria, a chorale, recitative and duet, closed by another chorale. He scored the work for three vocal soloists (soprano, alto, bass), a four-part choir and a Baroque instrumental ensemble of two horns (Co), timpani (Ti), two flauto traverso (Ft), two oboes (Ob), two violins (Vl), viola (Va), and basso continuo. The title page of the autograph score reads: "Festo Reformat. / Gott der Herr ist Sonn und Schild / a / 4 Voci / 2 Corni / Tamburi / 2 Hautb. / 2 Viol. / Viola / e / Cont. / di / J.S.Bach".
In the following table of the movements, the scoring follows the Neue Bach-Ausgabe. The keys and time signatures are taken from Alfred Dürr, using the symbol for common time (4/4). The continuo, playing throughout, is not shown.
Movements
As Hofmann points out, Bach achieved "festive magnificence", using two horns and timpani not only in the opening chorus but also as obbligato instruments in the two chorales. Bach established unity of form by using a horn motif from the first movement again in the first chorale, juxtaposed to the hymn tune.