I will try a clear answer , it begins to sound like something , a decent construction, in my mind .
I find interesting what is written by James Ellis :
Immediately following impact by a hammer near one end of a string in a piano, or plucking by a quill or plectrum in a harpsichord, a pure fundamental tone of the note is absent. Instead, all of the component frequencies of the whole tone are contained in a complex pulse-like wave that travels from end to end along the string, reflecting from one end to the other, over and over again, until it finally disperses into the discrete transverse standing waves that make up the timbre of the note,and persist for its duration. As explained above, when the string is struck or plucked near one end, the vector sum of forces produces a longitudinal as well as a transverse wave. When the complex transverse pulse reaches the termination at the opposite end of the string, it is reflected back inverted. A virtual inverted image of the initiation of the pulse occurs during the first reflection, and each following reflection is an inverted image of the previous reflection. This process continues until the transverse pulse has dispersed into discrete standing waves. A virtual image of the force vectors that initiated the longitudinal wave is repeated each time the transverse pulse is reflected, inverting at each reflection. If each reflection of this transverse pulse happens to be in phase with a reflection of the longitudinal wave, the vector sum of forces during each reflection will cause the transverse pulse to give up some of its energy to the longitudinal wave, causing the longitudinal mode to build up and the transverse mode to decay more rapidly than it otherwise would. The relative tuning between transverse and longitudinal modes required to make this happen is critical. The very slightest relative detuning of the two modes will cause this energy transfer to disappear.
That is why "noise" is indeed an accepteable terminology, but the tuner have some influence on the way it behaves,
This is in the way we build tone that those agreements are.
I begin to think we can have a tone that comes from the second partial (first) to energize the fundamental, or another construction with a more immediate raising of fundamental , that then adsorb and rule more partials.
That energy wave that contain the impact noise and excites the longitudinal mode (while using it as a vector (?)
we are probably dealing with it by the way we use some of the early high pitches produced by the lModes to energize our partials at the moment of attack.
Reading that the Lmodes (and their results hence quadra and other "phantom partials" are modified by the way the strings are coupling, sound logical to me.
I am may be totally wrong and only coupling of the transverse waves occur with the energy deal related to it.
I feel that the tuner is expecting to tune the "noise" - as it cannot be manipulated as it is he only can use the spectra and the energy dissipation to damp some part and enhance others.
I see unison tuning as being partly an energy regulation job
If we pluck the string to tune an unison the result will be very different, energy wise, than when the note is played.
But it is late !
I hope we can meet, for sure.
I will be there normally in March, but not at the end of February where I am going for a few days
An now I am going to bed (if you want to know !)
ALl the best
P.S may be it relates with the age of the captain too, finally
I suspect that we use the Lmodes (or the phantom partials) as a support for tuning.
It happened for instance on a G2 that I could not obtain a nice tone without playing extra FFF, then only the part of the tone I was waiting fort became apparent, and I could tune with some nicely ringing partials where before I only heard a dull and carboard like tone.
But the most surprising, particularely when one is used to get a justness approach via an ETD, is to see that one can provide a global tone, beat wise, that does not agree with the single, or multi partials analysis, using a richer tone including many unstable pitches that cannot be defined precisely, but add a lot of coloration.
(tuning with the sustain pedal engaged open the door to those pitches, as it oblige the tuner to take in consideration all available tones coming from the strings, when you have clean unisons with sustain pedal engaged, chances are that other vibrations modes than the vertical are taken in account)
I have done that once to a concert grand prior a recording, and the sound engineers told me thy did not understood what I did to the piano, that begin to be "singing like birds" they say.
AT another moment, trying to do a similar job I ended with too much beats to be acceptable, so there is a listening mode that may go along that trick to use it correctly.
And this can only be done with a non discriminating ear .
That is what I call "listening to the tone of the instrument apart" sometime possible in a small room as well, taking the inner reverberation in account when tuning unisons.
A too close listening is mostly good for recording sessions.
The tone can be cleared ans straightened to a point the L modes become too prominent and rob a lot of energy from the tone.
But I have always related that to a "tune the attack" job.