Ludwig Finscher describes the opening chorus of cantata BWV 121 as being "as archaic as the melody on which it is built is old". The melody is derived from a Christmas hymn of c. 450 AD and the very effective and beautiful opening chorus is in the style of a chorale motet (which was very much out of fashion in Bach's time). There's a very strange coincidence (and I'm fairly sure it is no more than coincidence!) lying in this movement. When I listen to this piece, I'm instantly reminded of the opening of the tenor line in the chorus Sein Blut komme uber uns from the second part of the St. Matthew Passion. The descending scales feel the same in texture and musical context. In the St. Matthew Passion this is, of course, the curse on the Jews for betraying the Redeemer. The Gospel for this day from St. Matthew? The same.
The cantata is concerned with the contemplation of the mystery of the Incarnation and the first aria, which has a delightful obbligato oboe d'amore accompanying and equally attractive tenor line, develops this theme. Following a recitative, the bass aria is a wonderfully upbeat, tuneful celebration of Jesus' coming. The final recitative calls for the poor soprano to hit a high B (a rare demand for Bach to make of his boys). The final chorale is a very beautiful conclusion to this cantata.
Copyright © 1996 & 1998, Simon Crouch.