All organ pipes can be mitered.  Stopped pipes can be mitred in 90-
degree steps; open pipes will sound better when they are mitred in
successive 45-degree steps.  The mouth ['top'] of a mitred open pipe
has to be kept away from the upper lip, or else they will influence
each other.

The material from which the pipe fronts are made is not of any
influence to the sound, so you can use any sort, even white pine.

Far more important is the way the boards are cut out of the tree.  All
material for wooden pipes should be quartered, or rift, or else they
will start to warp in short time.  The direction of the warping is easy
to remember: the annual rings of the wood tend to stretch themselves.
Don't underestimate this process!

When you make pipes of quartered wood it is not very important what
sort of wood you use.  Wood sorts with a fine structure are easier to
cut up than others.  Most European pipe makers are now using pear wood
or maple for pipe fronts.  It is, however, good to remember that the
great pipe voicer Carl Frei made wonderful pipes out of very inferior
materials in the nineteen-thirties!

Hans van Oost, Netherlands