Conservative Octaves?

[Bill Ballard]

On 10/19/96, TunerJeff@aol.com rote:
<<Is it just my opinion that matching the octaves (as far as possible)
help to re-inforce the power and (  ....hmmm... what would Braid-White or
Helmholtz say?.... ah!...just the word!...) sonority of the piano? >>

I'm sure that all of us tunaires feel this. I don't know how much of an
acoustical or mechanical basis there is for the glow that our freshly
done work takes on. Some of it must be that during the course of the
tuning, we've had the chance to hear each note and simply come to know
the piano. Another part is a matterof vindication, that at each step of
the way, we have set each note where it wants to be. Dogonnit, that
tuning sure sounds nice because that tuning is executed in the way we
want the piano to sound. If there is any voodoo in this business, this
must be where we first ecnoucnter it.

On 10/19/96, TunerJeff@aol.com rote:
<< Theconcept that the coincident partials, vibrating on the differing
strings, are actually helping each other can be experienced by 'ghosting'
notes... as many tuners do to hear difficult partials. Doesn't
over-stretching the octaves, to audible beats, lower the transfer of
energy? Couldn't this actually lead to negative re-inforcement or
cancellation possibilities between the partials (reducing sustain)? >>

I don't think we have to worry too much about frequency beating robbing
the piano of its sound. Certianly, the node of a beat rate is a point in
time where the amplitude is zero, and lterally, the sound is not there.
Remember  (as Del Fandrich has reminded us) that energy is not destroy or
creted It is simply tranferred. To visualize what happens to the motion
of a soundboard when is has to carry two frequencies which are within
15Hz, look at what happens to two strings coupled side by side to the
bridge. Should they have the same frequency, and should they be 180dgr
out of phase (ie., completely cancelling). the motion which they can
transfer to the birdge will be a net zero. But energy is not lost in this
instance. When these two strings find their motions coupled to a
motionless bridge, the bridge will appear to them to be completely rigid.
When their wave energy meets a completely rigid coupling, that energy is
completey reflected back into them. Thus, while one result of the bidge
(and board) carrying two strings with a difference tone beat rate within
the range where we perceive it as a separate pulse, is the beat ratein
which at periodic intervals, the sound energy disappears, there is
another result. That is, although at the node points of the beat rate the
sound has disappeared, the strings are not moving any less. Their motions
combine such that they together can't tranfer that motion to the bridge.
That energy in fact gets stored in their wavelengths until another part
of the beat rate cycle when their combination will allow the transfer of
motion to the bridge.

Don't ask me whether that means that the tone will be sustained longer
for all of that accumulated time when the two strings weren't able to
feed the bridge. Because I don't know. I am willing to bet that beat
rates don't make the sustain shorter.

There is of course another phenomenon, referred to by G. Weinreich in his
"Coupled Motion of Piano Strings" (SciAm, 1/79) in which two strings with
a frequency difference small enough will have their frequencies brought
into unison by  the motion which the induce in the bridge to which
they're both coupled to. I'm waiting for advice from Barney Ricca as to
whether this re-tuning by the bridge is of an order well below the 0.1c
which Jim Coleman Sr. has stated is out of reach of his hammer technique.
Until I hear from Barney, I'm going to lay awake at night, bug-eyed,
worrying about it. Face it, it's a world of illusions, a house of mirrors.

On 10/19/96, TunerJeff@aol.com rote:
<< Where do you believe such 'colorful' octaves belong? Specific pianos?
Sizes? Styles of music? Or simply a preferance of customer/clients and
individual tuners?  Certainly, there are as many styles of tuning as there
are tuners... but what's your view? >>

Well, for somebody else's view, Chris Trivelas suggests in an article on
unison tuning (PTJ 3/96) tha we use the contour/motion of a unison's wave
envelope to develope a consistency of susatin among notes in a region
(especially in the top 1/3 of the scale). Massage the unisons, as 'twere,
to find the sweet spot. He then asks whether octaves have a sweet spot.
Many of us myself included would say yes. I use the analogy of Sleeping
Beaty before and after the Good Prince's kiss as a comparison of still
and rolling octaves. She's just as beautiful either way, but I prefer her
warm and breathing as  opposed to cold and still.

Th irony is that sweetness in the unisons combined with sweetness in the
octaves produces a general over-ripeness of the tuning. It's a matter of
taste. So how much garlic do you like in your tofu stir-fry?

I agree that Dean, Jim Sr., Virgil and the entire cast have opened up a
wonderful topic.


Bill Ballard RPT
NH Chapter

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