A few months ago I pieced together a web page with information about
the Melville Clark "Apollo" expression piano system.  It includes facts
about the system, the tracker bar layout, information about service
manuals, and an illustrated summary of every known variety of Apollo
expression roll label.

Recently I added illustrations and more details about Melville Clark
himself, and I expanded the study of Apollo expression roll label types
to include Apollo roll labels which are _not_ expression rolls, i.e.,
the later "Apollo" rolls issued by Wurlitzer for their true reproducing
piano system.

The Wurlitzer system had been known under the name of "Art Echo" until
Wurlitzer took ownership of the Apollo name after Melville Clark's
death in 1918.  It probably sounds more confusing here than it should,
but if you're interested please take a look at my web site where you
will find a link to the Melville Clark page.

Regards,
Rob DeLand - BluesTone Music Rolls
http://www.bluesrolls.com