[ Ref. Bill Budenholzer in 170910 MMDigest ]

Bill, my first recommendation would be to reference Art Reblitz'
several books on mechanical music machines.  Contained therein you
will find all the answers you seek and more.  I'm not sure of their
availability on-line.

The Hupfeld and Mills machines were developed for different target
markets, with different economic scenarios and different artistic
temperaments.  Both machines are capable of producing exciting music.
The Hupfeld was designed with reproducing capabilities (piano and
violin).  I hope this information helps.

Frank Himpsl