[ Ref. Andrew Lardieri in 201217 MMDigest ]

Sheet music isn't terribly hard to find if you are willing to pay $10
or more for a copy. I just got 186 results for "Harry Akst" on eBay in
Sheet Music & Song Books - Vintage & Antique. I would expect similar
results for most other composers of the 1920-40 period.

The link https://yorkspace.library.yorku.ca/xmlui/handle/10315/580 is
potentially a very useful one since it is Canadian. Canadian copyright
protections are different from US ones. For US copyrights the cutoff
for 2019 is 1924, but this will soon change to 1925. The duration of
copyright in Canada is 50 years after the death of the author, so some
1970 music might be out of copyright, and a lot of pre-1940 tunes may
be in the clear.

For pre-1925 music, the Library of Congress website https://www.loc.gov/ 
is a great resource, as is the BandMusic PDF Library at https://bandmusicpdf.org/ 

I have never seen any substantial information on the sheet music
sources used by Wurlitzer (or Artizan or North Tonawanda) arrangers.
My assumption is that they were active members of various bands in the
Buffalo area, and had access to multi-instrument scores purchased by
those groups, and/or sold through various Wurlitzer music outlets.
These are much easier to arrange from than more common piano sheet
music.

There is a significant difference between rolls for band organs,
orchestrions and similar instruments and those for player pianos.
Piano rolls were typically created at a keyboard, while the others
were arranged on paper.

Wallace Venable