There have been occasions where a song has been recorded in C, but then frequency shifted to C#/Db to make it more awkward for other people to copy/play. There are probably other reason, too.

Historically, instrument tunings also varied, so different keys could have different characters. Modern equal temperament tuning mostly circumvents that.


Jazz relative beginner, starting at a much older age than was helpful.
Kawai MP6, Korg M50, Ui24R, Saffire Pro 40.
AVL:MXE Linux; Windows 11; Win8.1: Scarletts
BIAB2022 UltraPAK, Reaper, a bunch of stuff.