String coupling.

[Richard Brekne]

Robert Scott wrote:
> 
> Richard Brenkne suggests:
> 
> >I personally am convinced that if ETD would provide us information
> >about more then one partial at a time (as in 3 or 4) we could learn
> >an awfull lot about this process.
> 
> Here's the difficulty, Richard.  For an ETD to display tuning information
> about several partials, that ETD would need to have a target frequency
> for each of those partials.  Where should we get that target from?
> Current ETDs all use a tuning curve to specify the target frequencies.
> The tuning curve specifies the cents offset from a zero-stretch
> equal-tempered scale.  The tuning curve also specifies which partial to
> use for each note.  So we only have a target specified for one partial
> for each note.  If we were to display tuning error for several partials
> we would need to have an enhanced tuning curve that specified the
> stretch for each partial.  How would we go about generating such a
> curve?  We could use models of inharmonicity like the SAT (FAC method).
> But if any manual tinkering is required, can you imaging the complexity
> of the editing screen?  Instead of just one curve, there would be
> 3 or 4 curves.  Would you edit them separately, or would one editing
> operation move all curves simultaneously?  How would you make allowances
> for measured inharmonicity?

I am not quite sure we understand each other here... but perhaps you can
clear this up for me. Let me take an example as to what I am after. If I
take an inharmonicity reading of A4 then I have in effect a partial ladder
of reference frequencies. If I then compare A5's coincedents to this ladder
of reference frequencies, then in each case I can see how the coincidents
match up.. and adjust A5 appropriatly. am I right or am I right..??? grin.
In the same fashion one could compare and adjust A6 and A7 to A4's
reference partials, keeping in mind the decisions and consequences of
adjustments to notes already tuned. A combination of this kind of
information, and using the ear would allow one to build the tuning curve on
the fly at the same time as combining some of the best attributes of ETD's
with some of the best of the ear. Further.... it would be very very
condusive to makeing us much more concious of the interelations coincendent
partials have within the tuning puzzle.

This kind of usage for an ETD then relies on no predetermined or
pre-calculated curve. 

> Once you figure out how to generate a multi-partial tuning curve,
> then in principle it would not be hard for the RCT or TuneLab to
> have several spinners or phase displays (although, I would probably
> have to stop supporting 486's).
> 
> The desire to see several partials at once may have research appeal,
> but I doubt it would be of much day-to-day use.  If you don't mind
> using the same stretch numbers, you can quickly change the partial
> in TuneLab using the F3 and F4 function keys to take a peek. 

I do this all the time, but then when I use Tunelab, it is only to
reference previously Tuned intervals and use these references to confirm my
ear. For example, say I am in doubt about a particular 4:2 octave. (For
what ever reason) Referencing the 4th partial of the lower note, and then
tuning the 2nd upper to match gives an absolute perfect 4:2 octave. Further
its real easy to fudge wide or thin at need. I dont use the stretch numbers
in Tunelab at any time, and belive me Tunelab has taught me a great deal
about partials and how they behave in the context of coincidents amoung two
or more tones, how and why pianos need to be stretched, and what acceptable
parameters there are for varying degress of stretch. All this has helped my
ear tunings to a great degree.

> The only context in which this multiple partial thing came up is in
> regard to unisons.  And even the most ardent ETD fan will probably
> still tune unisons by ear (except possibly for the high treble
> where multi-partials are not an issue).
> 
Actually, I have heard and myself brought up the multiple partial thing in
other senses then unisons more then once. Grin.. this is just the latest
turn.


> If you really want to play around with multi-partial, do as
> Steve Fairchild has suggested and get several ETDs together, each
> set for a different partial.
> 

Grin... I am sure I have money to buy like 8 laptops and place to put them
around a piano and arms to carry them. Robert... I indeed look forward to
possibly meeting you in Arlington, and among other things paying you for
your shareware program. (I found out that sending you 50 dollars from here
would cost me another 50 dollars in bank fees, so I figured it was best for
me to just give ya da cash in person :)  )

> -Robert Scott
>  Real-Time Specialties

-- 
Richard Brekne
Associate PTG, N.P.T.F.
Bergen, Norway