The BandMusic PDF Library website includes the following information,
which I have edited slightly.

  "On January 1st, 2019, all musical works first published in the
United States in 1923 entered the public domain. ... This is the first
group of works to enter the public domain in the U.S. in many years.
Starting with 2019, the cutoff date for public domain music will
advance one year each Jan. 1.

  "From its beginning BandMusic PDF Library has been limited to works
published up to 1922; we will now expand our range each year, too.
If you have works for band published in 1923 (or earlier) that you are
willing to scan and share, please contact us."

The increase in public domain music is wonderful news in many ways.
For those few MMDers who work directly with sheet music, the BandMusic
PDF Library is a great resource, and if you happen to have old band
music, they are a great repository for it.

See http://www.bandmusicpdf.org/

Wallace Venable