This set of 5 variations gives a unique view at Buxtehude, first of all, at his skills as a composer. In the 2nd variation, all voices have changed place, compared to the 1st variation, so the bass becomes treble etc. I underlined this with the registration.
For the 4rd variation, this procedure is even more extreme: it not only changes the order of the voices, compared to the 3rd variation, it also mirrors them (so, if the treble melody ascends in the 3rd variation, the bass melody in the 4th variation descends). Again, the relation between the 3rd and 4th variation is underlined with the registration.
The 5th variation was added later, and has a very different character. It is not based on the text 'Mit Fried und Freud', but is a 'song' for the death of Buxtehudes' father. This moving aria, combined with Simeons' song 'Mit Fried und Freud' also shows Buxtehudes personal emotions and beliefs.