Also, speaking of Preuss, when I was looking for embezzlement, I found an account of how Fritz and Fredersdorf met. I had actually encountered that in a biography as a "this may have been how they met," along with "no one really knows" in other biographies, so I didn't share it, but Preuss is always interesting to me. (No source given as far as I can tell, and I guess I can't be sure it wasn't in the conditional, because god knows Google Translate misses that and I'm too lazy to check, especially in annoying fonts.)

Anyway. It may be the case that in December 1731, when Fritz was passing through Frankfurt an der Oder, and the local university students came to perform music for him, Fredersdorf was amazing on the flute, and Fritz went, "Him! I want him!" and got him out of Schwerin's regiment. Now, how Fredersdorf being in a student performance is consistent with him being in the regiment, I don't know, but perhaps selenak does.