A book was recently published, titled "Ethnic Piano Rolls in the
United States", Cambridge Scholars Publishing, May 19, 2021, Music
199 pages. It may be of interest to some.

At https://www.amazon.com/Ethnic-Piano-Rolls-United-States/dp/152756780X --
  Ethnic Piano Rolls in the United States Hardcover - June 1, 2021
  by Darius Kuinskas (Author, Editor)

"Ethnic piano rolls are an important part of a still-neglected musical
heritage. Having come to prominence in the first part of the twentieth
century, they encapsulate the musical life of several continents and
various ethnic communities based in the USA. This volume represents the
latest research on these unique and rare cultural artefacts."

A preview extract is at
https://www.cambridgescholars.com/resources/pdfs/978-1-5275-6780-1-sample.pdf 

Phil Dayson