I write in response to Jonathan Herz's enquiry about the stretched
tuning of musical box combs [140127 MMDigest].  The business of tuning
combs and the extent to which the upper and lower parts of the gamme
(scale or span) were stretched has also 'stretched' the imaginations
and research of so many for so long.

The late John Powell, a good friend of mine who worked in the same
company as me, had a good technical insight into vibration technology.
His research was published in the journal of a British musical box
society.  I also did a small amount of research that was published
in the book that I authored and edited, called "The Nicole Factor in
Mechanical Music."

Jonathan, you suggest that you may be making things too complicated.
I don't think so, because the choice is relatively simple although the
the subject can fill many volumes.  I hope I am not complicating the
matter further in the following account.

My engineering background, a bit like John Powell's, comes from my
limited knowledge of the tuning of musical instruments, historical
and otherwise, but leans more towards the practical analysis of the
mechanics of vibrating bodies, forced and induced.  What appears to be
the simple dynamics of a vibrating cantilevered piece of spring steel
is slightly more complex than may first appear.  Also, very little
attention has been given to the historical context in the way the combs
were made and tuned or to its receptor -- the human ear.

We know from historical accounts that Geneva was aloud with the
cacophony of the sound of musical boxes being tuned and played within
the overcrowded confines of its city walls and its high-rise buildings.
It was there some of combs were being ordered and made to a precise
tuning scale (the gamme) to suit the manuscript of the arranger and the
number of tunes to be accommodated.

Pre-tuned combs did not become the norm and practice moved towards more
standardised combs with sufficient teeth and dimensions to allowed a
particular gamme to be accommodated.  That was done by the addition of
lead weights for about two-thirds of the comb, hence lowering the pitch
with sufficient lead material that could be trimmed to raise the pitch.

Similarly, the remainder of the unleaded teeth had sufficient steel
thickness to thin the tooth and, particularly near the tip, also to
raise its pitch.  With good quality musical combs having anything
between 100 and 200 teeth, the work of comb making and tuning was
clearly complex.

By anticipating the required dimensions of the comb, the target
frequency of all teeth could be predicted to suite a variety of gammes,
thus minimising the work of tuning.  Combs were machined to incorporate
the anvils (platforms) for lead weights and spring dampers.  They were
slotted (early ones by hand) for the required length of tooth.

The comb needed a comb base.  Small early combs sometimes had an
integral base but for most cartel cylinder movements one was soldered
on.  At that stage all teeth had been cut so that they could accommodate
about 4 to 5 octaves, equivalent to the middle range of a piano.  The
middle 3 octaves would normally be for the melody and harmony part of
the musical score, with the upper (treble end) and lower (bass end)
for additional tonal effects.  There were many exceptions to this when
considering mandoline and forte piano combs so it is best to consider
stretching in terms of a single comb.

Paul Bellamy
Kent, UK

 [ Part 2 of 4 will follow tomorrow.  -- Robbie