For some reason, I always thought Jesu, Joy of Man's Desiring was mostly in G and had a G minor section.
I listened to it this morning instead of playing it on the guitar, and that performance (admittedly, I don't know where I got this mp3) was in F# and the minor section was in Eb (D#?) minor. Which seemed weird! That could just be my mishearing, though.
I found a
rendition of the original choral version, and it sounds like it's in G major with the dark middle section in A harmonic minor.
Thanks to the internet, we can see a
transcription from 1716. (It's the "Chorale" part.) The scribes listed are the Bachs J.S., J.C.F., and C.P.E. as well as Carl Friedrich Zelter. Zelter and the Bachs had terrible musical handwriting! Or at the very least, I find it hard to read in the present day.
This makes things more confusing for me. It looks like it's in D (two sharps on the left side of the staff) for the soprano, while the rest of the parts are in G (one sharp). No G# (which A harmonic minor would have) anywhere. Maybe I should try to read this more carefully. That'll have to be for another day, though.