I want to "start over" with my iTunes library. I originally started with all the family music, and so there is a lot of "cruft" in there that I now realize I will never particularly listen to. There are also hundreds of playlists, most of which I will never use again.
Also, since this iTunes library dates all the way back to Mac OS X Lion (or maybe earlier), it has carried over bugs with it: some of the songs stop playing before they reach the end of the song (reproducibly, every time) because something about the stop time got corrupted at some long ago date. (There's no way to find out which songs are affected except by playing every song, either.)
For these reasons, I want to actually "start fresh" not just delete a bunch of playlists and songs and continue using the existing library file.
Also, I want to keep the songs on disk that I plan to remove, but have them separate from my actual music collection.
What would be great is if I could open TWO iTunes Libraries side by side, one old and one new, so I could copy over playlists and such that I do want to keep. That's the title question.
However, based on this related question:
...I am pretty sure that the exact question about opening two libraries side by side is not possible. (Would be happy to be wrong about that.)
So, the broader question that I really need answered is:
How can I refresh my iTunes library in a straightforward fashion, retaining all my music files but omitting many of them from the new library (and retaining selected playlists but purging most of them)?
(Bonus points if I can preserve song ratings, play counts, and "date added" but I very much doubt if that will be possible without carrying over the buggy stop times, so I'm prepared to live without this part.)
I am using iTunes 188.8.131.52 and Mac OS X 10.11.6.