Responding to Craig Smith's article and Robbie's request, I have some
information regarding the system he saw at Vince Aveni's.
I believe he is referring to the Vince's Coinola X mandolin rail.
It is the first mandolin system I was familiar with, as a Coinola C-2
was the first coin piano Dad and I owned.
It is actually a wooden slat drilled precisely through the thin
dimension so that there is a guide hole for the notes on the treble
end. A metal rod goes through the hole with a wooden button each end.
The system is installed between the hammers and the strings and has
slotted holes in the slat which fit over pegs that allow it to move
left and right. When the music roll calls for the mandolin effect,
a pneumatic pulls the system to the right, placing the back end of each
rod in front of the hammer shank. As the note plays, the shank hits
the rod, throwing it at the string, which is hit with the front button.
The rod is returned by a light coil spring.
With the mandolin "off", the hammer shanks fly up between the rods.
The ones I have seen have been engineered to require the rod to hit the
string from momentum. In other words, if one gently pushed the hammer
fully, the rod would not be touching the string.
This is very familiar in the full size Coinolas. I don't know if it
was used in the Midget series. I am sending a couple of pictures to
make up for my lacking description.
Another variation on the hanging strip theme was that used in the
Nelson-Wiggens. I have seen a couple that appeared to be quite
original which used a pump type cloth with a thin (1/8") wood piece
glued on each strip. The few I have seen appeared to have the wood
directly between the hammer and string.
[Watch for the photos at the MMD Tech site,
[ http://mmd.foxtail.com/Tech/ -- Robbie]