It appears to me that after having been stopped for several years by Sonny Bono (rest his soul), the Copyright Clock has begun to click again. Works published in 1923 moved into the public domain in 2019, and the world has now resumed acquiring a new year's worth of music every year. The songs of the Great American Songbook will be coming into the Public Domain over the next two decades. I wonder if this will herald a rebirth of this wonderful collection of songs.
Here's the scoop:

https://fairuse.stanford.edu/overview/public-domain/welcome/

Ah, it's a wonderful time to be alive!
-Joe-