Re Sierra 10.12.6
Have been getting this message (see attached). It seems to happen when I open an older version of Finale (Finale 2011), but not sure if it's related to something else.

Is Xcode required by the System for something?

Looking this up, I saw other Finale users asking this same question in the past. Supposedly, after "Not Now" a few times the nag goes away and the program still functions normally.
If you still want, though, you should be able to Install just the command line tools without first needing to do the full Xcode install (which takes a very, very long time to download and install).

Thank you Chuck. I've selected "not now" and the program opens normally. It's an older version, and I have a recent version that isn't installed on the Sierra machine yet.

Incidentally - along a different line - my migration to Sierra included two older Adobe apps that are working, opened with no problems: Acrobat Pro 9, and InDesign CS4 (which I rarely use now, but want to keep it anyway.) Uninstalled Dreamweaver CS4 as I took my site down a few months ago. The only difficulty was trying to deauthorize on the older (2008) MacBook Pro. DW wouldn't deauthorize, but uninstalled anyway. Still working on InDesign. Will completely wipe the 2008 drive when am satisfied all is OK on Sierra - probably fairly soon.