Greetings Ted:  You will need something besides a squirrel cage fan for
pipe organ pipes.  Older forced air furnaces have high delivery volume
but at low pressures.  If you have the bottom two pipes from a rank of
pipes, very likely the 8' low CC will have the wind pressure written
somewhere on it, usually near the rank name and pitch stamping.  Your
blower will have to provide several inches of water pressure.

The player piano bellows is for developing a vacuum, not pressure.
You might give thought to vacuum operated percussions which are easy
to make.  I have a Link-built Glockenspiel and Xylophone for a theatre
organ that are electro-pneumatic and work quite well.  I have often
thought of converting them to play off music rolls as stand-alone
instruments.

Have fun with your project.  Being a first class woodworker helps.
Experience with pneumatics is also a plus.  See if you can locate
someone in your area to mentor you.

Al Sefl - Purveyor of Oddball Ideas... Like the pneumatic egg beater
that runs off your Hoover...