My book, "Player Piano Servicing and Rebuilding", has always included
the 1925 Duo-Art tubing diagram for a grand piano, drawn by John Morse,
since the first printing of the book in 1984.  You will find it on
pages 176-177.

When Harvey Roehl and I designed the book, he already knew that Vestal
Press would discontinue the many small reprints and pamphlets, and we
wanted to keep this significant drawing in print.  On page 174, you will
also find a schematic representation of the upright Duo-Art expression
mechanism with cutaway drawing of the inside of the expression box,
making it easier to understand how the theme/accompaniment system
works.

Art Reblitz