I'm enjoying Agatha All Along, but the least realistic part of that show is that Patti LuPone would be singing backup.
Seriously, I'm waiting for the Ballad of the Witches' Road (Patti LuPone solo version).
They did release a Lorna Wu version, sung by Seomoon Tak. It's very good, because she's an actual, you know, singer.
I haven't watched Agatha All Along yet, but the comment about it not being realistic that Patti Lupone was a backup singer triggered my "there's a song for that!" reflex. You might find this parody amusing.
Forbidden Broadway -- Patti Lupone/I get a Kick Out of Me