I would like to add my two cents worth to this discussion.  Nobody
has yet brought up the subject of blower characteristics or curves.
If you want to run an organ without control or a reservoir then you
must select a blower so that the pressure-volume curve is very flat at
the desired operating pressure.  This means that if you play one note
or twenty notes the pressure will vary only a little.  Many available
small blowers are the exact opposite to this: they have a very steep
pressure-volume curve.

The question, of course, is how do you find suitable blowers.  Whenever
you are offered a blower that you think may be suitable, get the part
number and do an Internet search to try and locate the pressure-volume
curve.

Alternatively I would suggest to go to the major fan and blower web
sites: http://www.ebmpapst.us/ is one of the better ones.  Examine the
curves to find a suitable blower, then do a search to see if you can
find the desired blower at eBay or a surplus seller.  It is amazing
what is out there.  If worse comes to worst you can always buy it from
a stockist.

You might find a perfect curve and blower but either the volume or the
pressure is not adequate, then run two blowers together either in
series or parallel.  If the blowers are cheap enough this is a practical
solution.

Phil Dayson