I have a nice tracker bar switch assembly, removed long ago from
an unknown 65/88-note player piano, that I plan to use someday with
a compact "10-tune" spool frame to play both 6/inch and 9/inch coin
piano music rolls at my foot-powered Pianola.

The switch assembly selects either a 65-note tracker bar or an
88-note tracker bar to operate an 88-note player piano action.
The machined brass block has two sets of nipples, all of 0.160 inch
outer diameter, arranged in four rows, for 65 hoses and 88 hoses
respectively.  Another set of 88 holes at the bottom of the switch
block received lead tubing connected to the 88-note player action.

The brass block, originally mounted on the rear of a spool frame,
is 15 inches wide by 2 inches high by 5/8 inch deep; it weighs
4.4 pounds.  On the back side of the block is a wood slat which moves
44 small sliding valve plates of machined brass, each plate with a
pressure spring to hold it against the block, and with airways for
two playing notes.  Two L-shaped hooks move the wood slat up and down,
which shifts all 44 valve plates together.

At the top middle above the brass block is the remnant of a wood
bearing for a horizontal rotary control shaft.  The shaft probably
had radial arms that engaged the lifting hooks.

On the wood piece at the top of the block is the neatly handwritten
inscription: "May 18, 1909 P. & D".  I don't know which brand of player
piano it was installed in, but surely it was expensive.

Robbie Rhodes
Etiwanda, Calif.

 [ I'll put the photo (and, later, a sketch) at the MMD Tech site,
 [ http://mmd.foxtail.com/Tech/  in the section on "Music Roll Spool
 [ Frames & Readers".  -- Robbie