"It has been noted that the original German hymn was characteristically a lively hymn of praise,"

Eh?

Down at my public library I once found a new book that discussed Bach's music and the society in which it was performed. In church, the high lines of music were sung by orphan boys who were raised in the most pernurious fashion possible by the town council. For example, citizens protested that the cistern of the boys' home had rats living in it, but the council did nothing.

So it's hard for me to imagine that when the young boys sang about being sick and sad that they did it in a lively fashion. Those kids knew about being sick and sad. Everybody did.

It's possible that when a cantata was performed, a woman was allowed to sing the high lines. That I don't know. But in the cantata, the hymn has to allow for the accompaniment, which is what most people think of as being "Jesu, Joy."

The accompaniment would have been played by a boy of about 16. It demends that he get three notes in every time the leads sing one quarter note. Plus it has chromatic accidentals coming and going. It's just not rational to make it go fast - or even moderately fast. Not only would it disrupt the religious experience if the kids crashed and burned, it would irritate the Duke. And nobody wants to risk that.

Meanwhile, back at the ranch, I like to play "Jesu Joy" on soprano recorder and pretend that I am 16 again.