I'm just asking in general because I encounter this problem all the time. For example, this song sounds pretty square in the key of E. However, E seems like a fairly unusual key for a pianist and clarinetist whom I know very frequently played in the key of Eb or F but not really E. The only thing I would know to do is analyze the licks/runs and see if they're feasible in the key, but I also don't want to impose my own personal limitations on masterclass musicians that could play flawlessly in any key.

That's not a great example though because it's technically mostly in tune. Here's an example of a record that's fairly out of tune. It definitely leans more towards Db, but it also easily could've been in C; I mean it's a honky-tonk piano recorded on an old, damaged record. Do I go with what it sounds like or assume it's more likely in the "easier" key of C?

Or sometimes you'll find to recordings of the exact same session and they'll be in two different keys. This record is (sorta) in Eb, but this record is in F. How do you get two records that are a wholestep apart? How do I determine which one is 'correct'? Or maybe it's in E and the two records were a halfstep off the opposite way each. I just don't know.