In MMD 981110 Alan Fox enquired about using an electronic tuning aid for
help with tuning musical box combs.

> I'd like to receive recommendations for a good ETA that can be
> used for tuning the comb of a music box.  Any music box restorers
> or hobby types out there who have successfully utilized an ETA
> to assist comb tuning?

I have successfully tuned combs using such a device but, unless
one is already quite familiar with the many varied aspects of comb
tuning to begin with, I would be quite hesitant to recommend trying it.
Nevertheless, I find my old and quite inaccurate vacuum-tube Strobotuner
very useful for this function -- but it is definitely _not_ a "plug and
play" solution.

I have no idea of how much experience Alan has, so I will make these
comments general.

First of all, it goes without saying that you should know what you
are doing before you start and the comb is actually _ready_ for tuning.
That is, it has been cleaned with great care and all dampers, pins,
etc., installed.  Any use of abrasives or files on the comb should be
minimal and done in such a way as to not adversely affect the tuning,
as bad as it may be at the start, in the first place.

Secondly,  one should be aware of the fact that practically _no_
musical box is tuned in equal temperament, which is today's standard
for musical instruments, and also that, unless the box is modern, the
reference frequency is almost surely going to be other than A-440.
Equal temperament and A-440 are the usual standards for ETAs.

Another situation regarding musical box combs is that the tuning is
almost always _very_ wildly stretched and, in some cases, particularly
in the bass, in less-than-obvious ways unlikely to be found on tuners
with preset "stretches."  This is because of large and uneven variation
of the overtones (partials) of the pitch of the comb teeth from the
true harmonics.

I have had success with the following procedure.  It is probably more
complex than necessary, but remember I am using that heavy little brown
box with the whirly disc and the neon light and my test equipment is
Paleolithic.  My actual standard is an inexpensive frequency counter.

The first thing I do is map out the scale of the comb.  That is,
I write down the actual fundamental frequency of each tooth as
I measure it.

In my case this is done by sounding the tooth (Surprise! the frequency
often changes as time elapses!) and tuning an audio oscillator to
exactly that pitch by ear.  This is the way I hold a pitch long enough
to be able to make measurements.  I then adjust the strobe to stabilize
on the oscillator and pluck the tooth again to confirm.  This is where
the shift in tooth frequency over time becomes more obvious.

Most combs are marked to show the tonic ("Do") note, and from this you
can determine the pitch to which it is scaled.  From here, using your
newly-prepared frequency map, you can go to the drawing board and work
out what the tuning should be, bearing in mind that it should not be in
equal temperament.  (I have had some success with 5th comma mean-tone).
This is the really tough part since you are presumably starting with an
out-of-tune comb.

Once that is done (quite awhile later, I would expect) you are ready to
do the tuning.  This is where the strobe can be very handy, but you do
not rely at all on its own built-in frequency standard.  Using your
oscillator and counter arrangement, set the strobe (using the "cents"
adjustment) to the desired pitch and tune away happily.  (Just a little
snicker here.)

One last note.  Your (hopefully golden- and not tin-) ear should be the
final judge, as with any tuning procedure.

Just my two-bits worth.

Jim Heyworth,
Sechelt, B.C., Canada
mailto:james_heyworth@sunshine.net