My experience in lowering the wind on an original band organ, which
I have done on a few for "in-house" use, is that the lower (larger)
flue pipes suffer first.  When voiced properly, brass trumpets produce
a beautiful, even mellow, tone/timbre, but typically sound more
obnoxious than loud (perhaps both, ugh!), as they are not typically
voiced optimally (or even close).

Clarinets or clarionets may be turned off, as the nature of that voice
tends to be piercing (nasal in my opinion).  Some octave ranks may be
disabled (high notes have a higher apparent volume).

Five inches pressure is pretty low wind for a band organ; I would
like to see how the pipes are made.  Perhaps the cutup is fairly low?
In any case, if necessary the cutup on flue pipes can be reduced quite
simply, and may be simply undone.

It sounds as though there are a few design issues with the machine.
In mechanical pneumatic instruments, l-o-n-g tubes are to be avoided,
as are overly "fat" (large OD) tubes.  Contact me if I may be of
assistance.

Alan Erb