I recently completed a 44-note calliope powered by a squirrel cage
blower.  The blower outputs air at high volume (around 250 CFM) and
low pressure (2" WG).  The air output volume is so high that there is
almost no perceptible pressure drop when valves are opened, so there
is no need for a regulator.  Furthermore these blowers are relatively
quiet, as they are powered by AC induction motors.  They are available
on eBay auction, where I got mine, for around $25.

The 2" WG wind pressure has proved to be more than adequate for my
calliope.  Take a look at my home page for pictures and a few mp3
files.

Regards,

Dick Partos