Recent items on tuning prompted me to find an old article I wrote
on tuning which may be helpful.  My own Wilhelm Bruder Soehne organ
restoration is progressing well.  It's a Model 79, 48 keyless, made
in 1926.  All the pipes have tuning slides!  It should be easier tuning
than so called 'fixed' tuning!

This is the method I use to tune.  There are probably other ways of
laying the scale but are probably more difficult.

  TUNING SCALE     in fifths and octaves

  C  to G above     2 beats flat
  to  G below       perfect octave
  to  D above       2 beats flat
  to  A above       2 beats flat
  to  A below       octave
  to  E above       2 beats flat
  to  B above       2 beats flat
  to  B below       octave
  to  F# above      2 beats flat
  to  C# above      2 beats flat
  to  C# below      octave
  to  G# above      2 beats flat
  to  G# below      octave
  to  D# above      2 beats flat
  to  A# above      2 beats flat
  to  A# below      octave
  to  F above       2 beats flat
  to  F below       octave - this to the first C should be 2 beats flat.

The last F should be played to the first C (the pitch pipe) and it
should be two beats flat.  If not, start again!

You may find you have to move your head around slightly whilst tuning
to hear the beats properly; it takes practice and concentration but
the beauty of this method is that you do not have to be able to hear
perfect pitches, as some lucky people can.  Just be patient and keep
doing it until the last F-C interval test proves correct.  Once this
initial octave is done the whole organ can be done in octaves to it,
a relatively simple task because you are then aiming for no beats.

Finish tuning the first single rank in octaves; it is a good idea to
try and make sure this rank is at the back of the organ.  If it were
at the front it could later get knocked out of tune whilst leaning over
it.  Work through similar size ranks first and proceed downwards
through the organ to the basses last.

Some stops, such as the Dutch bourdons and Unda Maris, are double ranks
where one of each pipe is purposely tuned either flat or sharp to its
mate.  In the case of Dutch bourdons, for example, the back rank is
tuned in unison and the front tuned sharp, usually about 5 beats per
second, although you can experiment with this beat rate until it sounds
nice.  The reed pipes are tuned last of all; they also are often the
most temperamental.

Andrew Leach

 [ The organ plays 43 notes, and the bass division is 'white keys
 [ only' (no sharps or flats), so it's a good candidate instrument for
 [ a well-tempered tuning method like this.  -- Robbie