(Photograph courtesy of Dick Hack.)

Manually operated control knob for the muffler rail in National automatic piano #7352. The knob is expertly machined, probably on a lathe or by an automatic screw-machine, and has a knurled rim to provide a non-slip surface that is easy to grip. A metal shaft (attached to the knob) penetrates the case and has attached linkages to both raise and lower the muffler rail (or one repurposed as a mandolin attachment).

(Photograph courtesy of Dick Hack.)

Muffler rail (or possibly a retrofitted mandolin effect) and associated linkage in National automatic piano #7352. Here the rail is in the raised and upward locked position. The rail consists of a metal rod bent at a right-angle at each end, with the two "tail" pieces flattened on the end and drilled for a wood-screw bearing and pivot point. When the lever arm's shaft (connected to the control knob) is rotated counterclockwise the rail is lowered. When the lever arm is rotated clockwise the rail is raised, and if and when it is rotated far enough, passing the over-center position, where any further rotation begins to lower the muffler rail, the weight of the rail itself keeps the lever arm pulled into the upward locked position.

(Photograph courtesy of Dick Hack.)

Close-up of the muffler rail lever arm linkage in National automatic piano #7352. Here it is easy to see that the maximum rotational arc permitted by the lever arm is limited by the rubber bumper (which consists of a long wood-screw inserted into a length of rubber tracker bar tubing). Rotational travel stops whenever the lever arm or the linkage rod to the muffler rail bumps up against the rubberized wood-screw. When the lever arm's shaft is turned counterclockwise the muffler rail is lowered, until the lever arm bumps up against the rubberized wood-screw. When the lever arm's shaft is rotated clockwise the muffler rail is raised until the lever arm reaches the over-center position, whereupon the muffler rail begins to descend. But this minor lowering is abruptly stopped when the linkage rod between the muffler rail and the lever arm makes contact with the rubberized wood-screw. This is a very simple but effective manually operated lock and cancel mechanism.

(Photograph courtesy of Dana Johnson.)

Manually operated muffler rail visible through the front glass in National automatic piano #7125. The muffler rail consists of a thick green colored felt curtain that is lowered between the piano hammers and the piano strings, thereby dampening the piano volume.

(Photograph courtesy of Dana Johnson.)

Mandolin attachment visible through the dingy glass window in National automatic piano #7274. This is probably a repurposed muffler rail, substituting the original muffler felt with a curtain type mandolin effect.

(Photograph courtesy of Dana Johnson.)

Bare rod for a muffler rail in National automatic piano #7524. There is a manual control knob located on the right hand side of the piano case. Here the felt for the muffler rail is missing, but the narrow action felt strips wrapped and secured around the rod still remain, and are used to prevent metal to metal clanking against the piano action bolts when the metal rod is lowered. The lock and cancel set of interlocking pneumatics at the far end operate the hammer rail.

(Photograph courtesy of Dick Hack.)

Replica lock and cancel pneumatics made for controlling a non-original mandolin attachment in a National automatic piano that has been factory retrofitted with a dog race diorama. The non-original mandolin rail is thought to have been made and implemented by a previous owner/collector. This recently made lock and cancel unit is patterned after the original factory made lock and cancel unit that controls the hammer rail. In this instance, the non-original mandolin rail is turned on (or lowered) when the soft vacuum level setting is enabled by the music roll, and turned off (or raised) when the soft vacuum level setting is disabled. The interrelated operation of the two pneumatics is simple: When the bottom pneumatic collapses the mandolin attachment is raised, whereupon it is then locked in the upward position by the large wooden hook affixed to the movable front side of the pneumatic. When the upper pneumatic collapses it pushes against the locking hook and disengages it, thereby allowing the mandolin attachment to be lowered. This is a good example of the kinds of well-intentioned (and often professionally executed) modifications that might be encountered in National automatic pianos.