The "O" roll scale I wrote about has a senior moment in memory.
Holes 15 and 16 that work soft vacuum to the snare drum also work the
pneumatic on the back of the stack to provide soft vacuum to the stack.

Go to my Facebook page and use that information for the "O" roll scale:
https://www.facebook.com/groups/178395399573009 

Don Teach
Shreveport, Louisiana

 [ "Treasures of Mechanical Music", by Art Reblitz, says the same
 [ but with different words:
 [   15 Low vacuum, piano and drums
 [   16 Normal vacuum, piano and drums
 [ -- Robbie