Back length tuning

[Mark Schecter]

Hi, Ric.

I think a lot depends on the nature of the backscale at hand. If it's a 
Steinway or Yamaha type of duplex, with one or two bars per section, 
there's only so much you can do, and that amounts to finding an average 
location that's nearest to some sweet spot of most intuneness.

I think it's a more interesting question when each note has its own 
moveable aliquot, such as my customer's '30's Baldwin concert grand with 
individual brass rods from tenor to top. The owner is a concert 
carillonist (really) but nevertheless, he noticed odd non-musical 
artifacts in the killer octave range, and upon investigation, we 
determined that the whole backscale was untuned. (The piano may have 
been restrung decades ago, before he bought it, or it may have been this 
way from the factory, but we'll never know for sure).

I spent a couple minutes on his grinder adjusting the shape of a piece 
of 1/4" brass rod into a "tool", then together we started moving 
aliquots until the sound of the harmonic made sense with the speaking 
length. (This was not possible in every single case, due to insufficient 
available space). We concentrated on octaves 5 and 6.

Immediately, after about an hour's work, we noticed a reduction in 
jangliness, and improvement in clarity. A small cloud of background 
noise had dissipated, and several months later, he continues to feel the 
work was well worth it.

The other interesting case I've seen is Fazioli. They also use an 
individual aliquot per note, made of triangular brass rods that they 
call "triangolini", Italian for, guess what.

They spend hours on every piano tuning these very exactly in a laborious 
iterative cycle, using an etd. It goes something like this:

1 Tune the speaking length as usual.
2 Set the etd to whichever partial this note's aliquot will be tuned to.
3 Pluck the back length, watching the etd to determine whether the back 
length is flat or sharp.
4 Tap the triangolino (that's the singular) to move it
5 Retune the speaking length to match the (unchanged) etd.
6 Repeat 3 through 5 until you're satisfied. I think the standard they 
use is, etd stopped, so they're not tweezing for illusions; they make 
the duplex match the harmonic.

Without A-B'ing two identical pianos, one with tuned and one with 
untuned backscale, I can't say definitively, but I will say this: 
Fazioli pianos have a very clean, powerful, unadulterated sound. When I 
overlay that on my experience with the Baldwin cg, I think I see a 
pattern emerging. It just makes sense to me that having a large number 
of untuned open lengths at liberty to sympathize with any stimulus 
whatever is a recipe for random noise, otherwise known as unmusical 
sounds. Organizing those open lengths does make a difference.

One last point. I have tuned a small number of Yamahas in recording 
studios, which prior to my arrival had had their duplex scales stripped 
out, I'd imagine to reduce extraneous noises when close-miking. Without 
exception, those pianos sounded less bright, less interesting, and less 
musical to me than the large number of similar pianos I have worked on 
with backscales open and functioning. My conclusion from all of the 
above is, it makes sense to tune open lengths where possible; and, if 
extraneous non-harmonic sounds are a problem, and you can't tune them, 
try silencing them.

Hope this helps.

-Mark


Ric Brekne wrote:
> Hi folks
> 
> I would really appreciate hearing a bit about varying methods of 
> <<tuning>> the back scale of instruments.  Anyone with knowledge of 
> Duplex Dans methods, other  approaches, basic tuning methods that 
> perhaps address the back scale in anyway would be very nice to hear from.
> 
> My basic understanding at present leads me to believe that the front 
> duplex can be tuned to the detriment or enhancement of both sustain and 
> tonal qualities if tuned slightly out of tune with the speaking lengths 
> and that this applies to a much lesser degree to backlengths.
> 
> Any discussion, info, etc would be greatly appreciated.
> 
> Thanks
> RicB
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