I've long wondered if anyone actually favored the sound of an
out-of-tune piano.  I now have my answer.  As illegitimate as that
sound is to a piano tuner, I must concede that if some listeners
prefer it, and it has a cultural pedigree (no matter how motley),
and a unique quality of tone, then it creates its own legitimacy.

In writing and speaking, it is a cliché that "usage determine
correctness."  The same must apply here when viewed from the longer
perspective that different sounds attract the ear.  Caribbean steel
drums have a similar twang to them--although they are more properly
tuned--and no one can really argue that it is an illegitimate
instrument.

Having read the preceding, interesting posts, I would like to offer
my own perspective: a "honky-tonk" sound is nothing more than the
result of years of neglect and use of a piano.   Pianos go out of
tune in a somewhat predictable way, and it would be hard to imitate
this but not impossible.

A piano that has not been tuned for about twenty years will usually
be one-quarter-tone to one-half-tone flat; a piano that has not been
tuned for forty to fifty years will be one whole-tone flat.  19th
century pianos, with less-resilient wire, end up a minor-third flat.
I've never encountered a strung and chipped 20th century piano slightly
flatter than a whole tone.

Pianos go out of pitch across the soundboard in a regular way, also.
The bass bridge is much closer to the rim of both uprights and grands,
and thus changes pitch far less than the treble bridge.   The low
tenor on some verticals also does not change as much because the tenor
end of the treble bridge approaches the edge of the rim (the bottom
edge of the strung back).  Very high treble strings also go out of
tune less.  This does not mean that these strings never go out of tune,
but comparatively less so.

The center of the soundboard is most flexible, and normally will vary
in pitch the greatest of any section in a piano, but as stated in
a previous discussion, the mid-treble (notes 52-70, roughly) can be
the most out of tune of all.

Add to the general sagging in pitch the fact that unisons seem to
de-tune unevenly as well.  I've never read any definitive claims on
this phenomenon but I think that one or both of the outer strings of
a unison detune before the center one.  Since the bridge pins for
these strings often stand proud of the adjacent chamfer, I suspect
that they are prone to more shifting with the bridge.

I have no proof for this hypothesis.  It's also possible that the tuner
(me?) becomes less diligent when tuning the outer strings of the unison
to the center string, and thus the torqued pin rebounds noticeably.

Older pianos, with stressed pinblocks, will have some pins that are
looser than others, which allow such strings to de-tune more than the
others when the piano goes through multiple cycles of drier humidity.
This accounts in part for the irregularly sour nature of a "honky-tonk"
sound.

As for pianos shipped to saloons in the mythic Old West, these
instruments would've been tuned once at the factory, then shipped out
by train.  The sagging pitch would've happened almost immediately and
dropped almost one-half-step by the time the piano arrived at its
destination.  It takes two years for music wire to stabilize under
tension, and the instrument will quickly go flat if not tuned at all
during that period.  See paragraphs 2 and 3, above.

So, if one wants a honky-tonk sound and does not want to wait forty
years for it to naturally occur, the piano could be tuned without any
stretch, actually with slightly shrinking octaves in the treble, sloppy
unisons that are sort of close, and random and occasional strings that
are one-quarter-tone flat; that should just about do it.  Old, worn,
grooved, hammers, without further modification, would certainly add
the finishing touch.

Mark Ritzenhein