The important differences in tone quality and regulation, depend
upon the fine art of voicing.  Given a particular pipe construction,
a skilled voicer can obtain a spectrum of different qualities of tone.
He/she will, in voicing a rank of pipes, make adjustments such that
one would not be able to adequately measure them with calipers, gauges,
etc.

Only your ears will tell you.  When final voicing, if your adjustments
(except nicking) go so far as to make a _visible_ difference, you have
gone too far.  Dan Garland taught me that.

Numerous factors affect the tone of an organ pipe, and a good voicer
will plan these to be cumulative.  The materials are less important,
because they affect the tone far less than dimensions of the mouth,
upper lip, and windway.  (Ross King taught me that).  The cut-up and
width of the mouth have arguably the greatest affect.

But there's more.  The number and depth of nicks in the languid/block,
and in the particular case of violin pipes, the shape and adjustment
of the frein; and the size of toehole.

The scale of a pipe (it's cross-sectional dimension) has less affect
than most organists realize.  Scale is only a starting point establish-
ing tone quality only in a general sense.  A Diapason pipe can become
a Flute merely by blowing more gently, or by simply raising the cut-up.

From a string pipe (which is overblown), one can produce a decent
Quintadena by adjusting the toe hole and frein just a tiny bit.  A
little less, and it is a Nachthorn; less still and it's a Dulciana.
(None of these constitute the best, which requires multiple
adjustments.)  I could go on....

At this point, I should refer my colleagues to a book on the voicing
of organ pipes.  But working inside an organ with a professional voicer
is the truly best way.  I am grateful for the experience and commend it
to anyone genuinely interested in producing a well-voiced organ.

Regards,

Robert Linnstaedt