Does anyone out there have any information on who actually developed
the expression system used in the Melville Clark "Art-Apollo", Amphion
"Dynachord" and Price & Teeple "Art Symphonola" expression pianos?

They all came out in about 1915. Seeburg started using the
system in their Seeburg "Xpression" piano in about 1918. They played
"Autograph Automatic" rolls from QRS and "Apollo X" rolls from the
Clark Orchestra Roll company.

When they were first put on the market their advertisements all claimed
credit for the design. All three firms had good engineers capable of
doing the design. Amphion claimed they had been working on the system
for about four years. It's possible they pooled their individual patents
and designed the system jointly.

Rich Schommer
Alliance, Nebraska

 [ Art Reblitz described the Art Apollo expression roll scale at
 [ https://www.mmdigest.com/Gallery/MMMedia/QRS/Apollo/pianos.html 
 [ -- Robbie