[ Bill Clark wrote in 101017 MMDigest --

> Are there guidelines on how to lay out the pipes? ...

Hello Bill,  I'll try to give some generalities although I'm sure that
the professional folks will have much better and more detailed ideas.

In the traditional and antique organs, there can be one or more
windchests.  In general, the primary windchest for the melody, etc.,
consists of a series of channels that run fore and aft in the organ.
Each channel represents a note.

In the simplest case, the pipes are mounted directly to the top of each
channel and each channel may have more than one pipe reflecting multiple
ranks of pipes.  Wind is supplied to the channel from a valve controlled
inlet such that the pipes sound when the valve is opened.  All pipes on
the channel speak when air is supplied.

You ask about whether they should be chromatic.  This depends on the
organ, of course, but I assume that what you are really asking is
whether the pipes are lined up in note order or in a mixed arrangement.
The answer is that the pipes, and therefore the channels, are usually
arranged with the tallest pipes in the center and tapering to the
shortest pipes at the outer ends.

This is solely for the reasons of appearance as viewed from the front
of the organ.  I have seen some organs where the pipes are simply lined
up across the organ in order of the notes.  For a homebuilt organ, you
can choose your own preference.

The separation between the channels of the chest will depend on the
width of the largest pipe you install on it.  There have been discussions
about pipe interference but I don't know of any definitive rules about
locating adjacent pipes.

Bass pipes are generally located in the bottom or the rear of the
organ.  Reed bass pipes may be located on top but generally at the rear.
Accompaniment pipes are frequently located on the left and right sides
and may be in line with the melody pipes.  In this case, the melody
pipe cascade would be located in the center and the accompaniment pipes
can be on the same windchest but spread in locations to the left
and right sides of the melody.

By "dog whistle flutes" I assume you are referring to Piccolo pipes
in the melody.  These are usually located in front of the other melody
pipes.  Countermelody pipes such as trumpets, saxophones or baritones
should be located where they can be heard well but not overpower other
melody pipes.  Wurlitzers usually have the trumpets on top while many
German organs have wooden trumpets in the front but facing down toward
the ground and often behind a section of facade.

I hope these comments are helpful.  Let me know if there are any other
questions.

Regards,
Bob Conant
Bradenton, Florida