The foregoing pages have dealt with the fundamental principles of pneumatic piano playing mechanism and have explained the physical laws involved, together with their application to the subject under discussion.

I now proceed to a description of some leading mechanisms now on the market and in use.

It has of course been impossible within the limits of my space to make separate description of every extant player mechanism, and what follow is intended only to emphasize the individualities of the leading examples.

This part of the work is especially intended for the use of tuners and repairmen, as a guide to them in the work of regulating and repairing, and above all, as a sort of map whereby they may acquaint themselves with the ground they are traversing when they undertake to explore unfamiliar players.

It is impossible in a book like this to emphasize all the various claims put forth by manufacturers, and my intention in this part has been merely to afford the practical information, gained through personal contact with the mechanisms described, which may be desirable for the purposes indicated above.

The mechanisms manufactured by this company and known as "pianolas," are for the exclusive use of the AEolian line of grand and upright pianos. In addition to these, the AEolian Company continues to manufacture a certain number of exterior playing mechanisms of the cabinet type, which are used considerably in foreign countries.

The mechanism produced by this company is made in their own factories and contains many original features which have given the Pianola fame. The name Pianola has become an almost generic term for player-piano, although it is the exclusive property of the AEolian Company. The Pianola is noted for its originality, its high class of workmanship and for its distinctly artistic character.

The interior Pianola mechanisms are of wide variety in constructional detail, although following the same general design. The entire ^Eolian line of grand and upright pianos is fitted with one or another style of these Pianola mechanisms, each especially adapted to its particular purpose. Description must therefore be somewhat general.

Bellows-System. The general Pianola design is of the indirect variation type with single equalizing unit, the expression and motor governors being usually carried on the inner action. Special folding pedals are used, and in the grand Pianola mechanism these fold up inside the lyre box, which also carries the exhaust units.

Pneumatic Action. Both the double and single valve systems have been largely used in Pianola practice. Older models were built with pneumatics and valves below the key-bed, but this method has been superseded for several years by the modern plan of placing me playing system in front of the piano action. In the grand mechanisms the pneumatic and valve system is housed beneath me key-bed.

Tracker-Box. In upright mechanisms this is placed above the pneumatic action. Carries tracking device, uses rubber tubes, and has metal bar fitted with marginal perforations for automatic sustaining pedal, and Themodist (automatic accent). Metrostyle (tempo guide) pointer is carried on tempo indicator. Switches for Themodist and automatic sustaining pedal also carried on tracker box. In grand mechanisms, the tracker-box is carried behind the fall board. Some models have combination 65 and 88 note scales.

Motor. The typical Pianola motor is of the Pneumatic 6-point type, having three double units. This arrangement was originated in Pianola practice and has been very successful. Older models will be found with three point motors. The gear shift and action cut off on these have always been of the direct mechanical type, lever manipulated. In recent practice a three-way control of the rewind lever has been adopted.