[pianotech] Stretch in tuning

[John Ashcraft]

Terry,

Stretch is inevitable from all the test intervals, as you noted. The
interval one chooses to use determines the stretch. Many tuners use a 6:3
octave in the bass, a 4:2 in the middle, tapering to a 2:1 in the treble.

I went to a chapter meeting when I was much less experienced, and the RPTs
were touting 10:5 and 12:6 octaves in the low bass, describing the more
powerful sound they got. So, the next piano I tuned was an average American
console for an elderly lady . I carefully went to 10:5 octaves in the
second octave and 12:6 in the lowest. I got a call a few days later. She
didn't like the bass. Actually, I didn't either, but my expert friends had
said that it would sound good. Of course, they were not saying that this
console needed that treatment. I re-tuned the bass back to 6:3 at the
bottom, and the lady and I were happy with the result.

I check out the lower 2 octaves by ghosting: depress A13 and A25 without
letting the hammers strike. Then play A37, E44, and A 49 as moderately
short *forte* staccato notes. You are setting up the tests for 4:2, 6:3,
and 8:4. If these harmonic tones ring but don't beat, you are at 6:3. If
you are closer to 4:2, the A49 will beat, so your A13 is sharp. If the A37
beats, you are flat with the lower note.

If you are using the ETD all the way down, you look at the harmonics at the
4:2 note until you get to the last 2 octaves, then switch to the 6:3. You
may find, as I have, that your ear is better and faster than the ETD. The
piano truly will tell you where the best octave is. I am not saying that
6:3 always works in the bass, but it is the interval I use far more than
any other.

My take is that you don't add stretch beyond that which the tests tell you.
However, with the variety of tastes we encounter, there must be those
tuners and players out there who like more.

John Ashcraft, RPT

On Fri, May 25, 2012 at 6:35 AM, tlneely <tlneely at mindspring.com> wrote:

> Hi all,
> As we all know, when tuning up and down from the temperament, octaves are
> stretched from the theoretical pitch of pure octaves as one might find
> on a pipe organ due to the piano being an inharmonic instrument. We
> determine this expansion based upon test intervals and "let the piano
> tell us" how much it should be.
>
> For years at conferences I have heard respected folks discuss that
> you have to "stretch the octaves". Everyone nods their heads wisely,
> and the discussion moves on.
>
> My question is this- Is the stretch being discussed in addition to
> that indicated by the tests? Should one do this. If so why and how much?
>
> I suppose I should confess here that I learned to tune aurally on
> harpsichords
> and fortepianos where the inharmonicity is much less than in the piano
> (using
> equal beating historical temperaments). I use an ETD for piano work(have
> owned
> most all of them over the years).
>
> Thanks,
> Terry Neely
>
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