I built a John Smith Busker organ and have had a great time with it.
Now I'm working on building a better instrument of my own design.
I will stick with the 20-note format, since I've got a few rolls
already and it seems reasonable.

I have been reading two books on street organs, one English and one
German, and both show a two-stage relay scheme.  The first relay has
a bleed valve and is operated by the hole in the paper.  That stage
then sends its air to a second pneumatic which operates the valve in
the wind chest.

Why does it take two stages?  Why not just let the air out of the
primary relay blow the pipe directly?

Ron Ginger