Bill, there is an excellent book, "The Violin-Playing Machines",
by Q. David Bowers, comparing the Hupfeld Phonoliszt-Violina and
the Mills Violano-Virtuoso.  It was published in 2012 by AMICA:

http://www.amica.org/Live/Misc/Sales/Books/Violin-Playing/index-SOLD-OUT.htm 

Al Menashe

 [ A sample of a few pages from the book is at
 [ http://www.amica.org/Live/Misc/Sales/Books/Violin-Playing/Violin_Sample.pdf 
 [ For sale at
 [ https://www.biblio.com/book/violin-playing-machines-hupfeld-phonoliszt-violina/d/987824658 
 [ -- Robbie