One can tune a pipe organ from an electronic tuner very well if it is
done right.  I do it all the time.  Use no stretch in any pipe organ.
You may stretch the bass of a Theater organ if you like.  I usually
do not, however.

I tuned pianos from the fork for 10 years before I tuned organs for
customers.  At that time I had no assistant so the church secretary
held notes for me.  It was fine if she knew the keyboard, but most
of them didn't.  I discovered that if I bought a Korg tuning standard
I did not have to teach her what a fourth, fifth or third was.  I have
been using the Korg for the last 20+ years.

Begin tuning with the 4-foot principal, diapason, octave, montre, or
whatever it is called.  All of these names refer to a principal organ
pipe.  Tune from Tenor C (one octave from the bottom of a 61-note
keyboard).  Use the tuner to tune two octaves of notes.

At that point, have your assistant hold the note to be tuned with
the octave below, going all the way up like that.  Then start back at
Tenor C with the octave above (middle C) and tune going down.  You now
have the tuning stop for the rest of the whole organ.  I usually start
at low C and tune each rank to the tuning stop.

The electronic tuner is useless for anything but the center two octaves
of the tuning stop.  You usually cannot start at the top of the rank
as your ears have to become accustomed to the fast beats.  Begin from
bottom to top on each side.  Many chests are C side and C# side.  These
require going up the scale in whole steps -- C, D, E, F#, G#, A#, C and
the other side -- C#, D#, F, G, A, B, C#.

If the organ is 300 ranks, you still use that one stop to tune every
stop.  The only exception is if you are too far away from it to hear
it or if the chamber walls are too thick to hear it.  Then you can set
a new tuning stop in that room -- a 4 foot principal if possible --
and tune that whole division to that stop.  You never have more than
two pipes playing at once except on mixtures, but that is a whole
"nother" chapter.

You can take these guidelines to tune any band organ, as I have
done so for as long as I have tuned church organs.

D. L. Bullock -- Piano World -- Dallas Pipe Organ Service -- St. Louis