„Pianola“ instruments have been offered in a large variety of different designs - technically as well as cabinet-wise. Customer demands, competitor moves as well as technical and patent issues fostered a wide portfolio of different types of "Pianolas". The basic principles of a player piano are more or less the same.

To differentiate between the types of a player piano, here are some characteristics:

 

Version (Cabinet, push-up player, built-in piano and/or built-in grand piano)
Design (Pedal-Piano, Artistic Piano, Reproducing Piano)
Scale (number of holes at the tracker bar) and
Style (varies by manufacturer: Aeolian, Hupfeld, Welte, etc.)

The following overview shall help to understand some basics of this interesting "world of pianolas". There are extensive books, webpages etc. around this topic - please ask for recommendations in case you want to learn more. Additions, corrections, remarks are very welcome.