The fourth part of Bach's Christmas Oratorio was written for the Feast of the Circumcision. It is, in a way, the most perfect and symmetrical of the six sections of the oratorio The two horns give a peaceful, otherworldly quality to the opening and closing choruses. Next comes a section of gorgeous recitatives by the bass, with the sopranos intoning a chorale. This is among the most beautiful of all the chorales in the Christmas Oratorio. It is interesting that in this segment of the oratorio, all of the chorale tunes are by Bach and were unfamiliar to the congregation; clearly Bach meant the chorales in the segment to be poetic rather than congregational. Next comes the stunning and popular "echo" aria for soprano and oboe; for all of its simple, almost popular quality, the relationship between the obbligato, the voice, and the echo is complicated and unpredictable. the soprano chorale returns with the bass recitatives. Then comes a vibrant and rhythmically irresistible tenor aria with the violins. The final chorale brings back the radiant horns to close this wonderful, treasurable work.