Pure 12ths tuning

[John Formsma]

These questions are for Bernhard Stopper, but I thought they might be
interesting for the whole list.

I was at your presentation Saturday at the PTG convention.  It is a
fascinating concept, but one that I'm not quite sure about just yet.

Please tell me if I understand the concept correctly. (I'm a concepts
kind of guy, and like to first understand the logic behind a system.)

I understand your goal is pure 12ths, and you begin aurally by tuning
D3-A4 as a pure 12th. If you have pure 12ths throughout, you will of
necessity have wider octaves and purer 5ths  (along with wider M3s,
P4ths, M6s, etc.). What I'm wondering is if it's possible to arrive at
the same conclusion (Pure 12ths) by merely starting the tuning with
wider octaves?

In other words, you could get the same result...just working at it
from the other direction (wider octaves) rather than beginning with a
P12th. Both roads would lead to the same place.

It would seem that if you are comparing your Pure 12ths tuning to the
first temperament octave of a 2:1 or 4:2 size, your method would be
preferable in most pianos. This is because most pianos will sound
better with a greater stretch than a 2:1 octave in the temperament
region.

But many of us are already tuning with temperament octaves wider than
4:2, and we end up with pure 12ths as a result.  We might therefore
might have a tuning that matches yours, but have arrived there by a
different road.

Your thoughts?

Also, could you briefly explain how your program picks out the stretch
that a piano is supposed to have? How much partial information does it
measure before calculating the tuning? Does it automatically adjust
the optimum stretch, or do you have stretch options like the RCT?

On the Fazioli you tuned, which sounded very nice (musically), I
noticed some 12ths that were actually wide, and some double octaves
that were also quite wide (up to around 2 bps). I think the wideness
was around G4-G6, but it might have been G3-G5. Wherever it was, there
 was also jump in the beat speed of ascending chromatic intervals
(like the M17s). Would that be attributed to the tuning program, or
instability in the piano?

Thanks,

John Formsma