[pianotech] Beyond octaves

BobDavis88 at aol.com BobDavis88 at aol.com
Sun Mar 15 18:13:42 PDT 2009


A lot has been said about aurally pure octaves,  but no matter how one 
produces them, they are worth only so much by  themselves. A few thoughts:
 
1) There is, especially in the octave 5 & 6  area, a window of a cent or so 
above and below a centerpoint, in  which the octave sounds "beatless," just a 
little different in color, as the  upper partials begin to break away, but 
before there is the heavier sensation of  a beat lower in the partial coincidence 
ladder. It is easy to have the upper  note too low and be fooled into thinking 
it is clean enough to leave alone, but  there is a point at the top of that 
window where the octave starts to sound a  little silvery, and that works 
better with the necessary stretch than the same  point below zero, even though they 
sound about the same, and even though a beat  isn't apparent.
 
2)  The cleanest octave might not be the  best. I have heard tuners, Virgil 
Smith among them, claim that they tune  "beatless" octaves, double octaves, and 
triple octaves. The octaves  etc. were nice enough, but they certainly 
weren't beatless, or even at  maximum cleanliness, to my ear. I don't think the laws 
of piano physics  permit it. On most pianos, a triple octave at the point of 
least noise will  force the single and double to be above the point of least 
noise; even  slightly above the "beatless-but-silvery" point. I know that's  
not news to most tuners, but all the talk of beatlessness merits a  reminder. 
The nature of the inevitable compromise varies with the pianist,  the piano, and 
the venue, and is where the art lies.
 
3) Especially in shorter pianos, or pianos with  uneven voicing, a "clean" 
point can be hard or impossible to find in the  bass. Here's where the ability 
to isolate partials individually can be helpful.  Because different partials 
may be prominent on adjacent notes, tuning to the  quietest place in the octave 
can cause uneven double octaves, even to the point  of an objectionable beat. 
It makes sense to follow the beating at an individual  partial (for instance, 
the 10:5 coincidence, which is fast enough  to compare easily). Keeping track 
of evenness of progression (as at least  one input) can help split the error 
musically, and prevent too much irregularity  in double and triple 8ves, which 
may be more audible than a  not-perfectly-clean single 8ve (I suppose you 
could just voice out the offending  partial).
 
4) Every note is a member of many  intervals, and an improvement in one 
interval always comes at the expense of  another. Treble or bass, I think that 
intellect complements intuition,  although I agree that we are all different, and 
it doesn't matter how you  get there - it sounds great or it doesn't.
 
Bob  Davis
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