Was Gott tut, das ist wohlgetan III, BWV 100, first performed in Leipzig in 1734, draws together movements composed almost a decade apart. The opening chorus dates from September 1724 when it was written as a chorale fantasia for BWV 99, a work of the same name that sets the same hymn by Samuel Rodigast. For BWV 100 Bach adds two horns and timpani to the strings with flute and oboe d’amore in BWV 99. Bach continues the words of the title chorale unaltered through all six verses while managing never to repeat himself musically nor to allow the hymn tune to outlive its welcome. Bach has set himself a new challenge, to provide maximum variety within the constraints of the verse form. The four middle movements, composed in the early 1730’s, are hugely challenging and gripping, without a single recitative to break up the pattern.
The alto/tenor duet seizes upon the image of God leading us on a ‘right’ path in both the vocal and instrumental writing. The repeating bass line climbs nine notes up the scale before descending and climbing again towards the cadence. Likewise, the alto and tenor imitate each other singing a rising fourth on each entry of new text.
The soprano aria with fiendishly difficult flute obbligato invokes the metaphor of God as a physician who would not pour out poisonous medicine for us. Yet the flute motives clearly suggest the gurgling of the noxious potion.
The jaunty aria for bass and strings, with lilting syncopations in the 1st violins and urging runs by the 2nd violins, all convey an unequivocal message of joy and steadfast faith in tandem with the text. The final aria for alto with oboe d’amore is a gentle siciliano, which describes the bitter taste of the cup referred to in the soprano aria and how its sweetness lies concealed.
The final chorale goes back even further to 1723, where it formed the closing movements of both parts of BWV 75, the first cantata Bach presented in Leipzig and reveals quite a different approach from the opening fantasia. The original version from BWV 75 was scored for two oboes, strings and continuo. The addition of the horns allowed for an imitative entry of the second horn and winds. But it takes an extra bar to fit this in, resulting in a slightly larger scale than the BWV 75 model.