Playing all three M's together sounds pretty weird.
then the tuning has been messed with by some 3rd party
but there is no sense to the frequencies of the H register.
sometimes an extra M in unison (or damn close to it)
is what some pro's want for a very clean and pure
solo voice, but richer without actual noticeable wave,
with the third M reedset dcausing pretty much ALL the musette
my Excelsior 960 (LMMMH) two of the M's are unison a-440
while the third M gives a gentle (full chord) musette
So how would you go about tuning something like this?
first, decide on your base/reference frequency by
analyzing the L set and tune the MIDDLE octave of the L reeds
next, tune the primary M low octave of reeds exactly to the
same frequencies, then put the 2 sets into the accordion and
make SURE the second octave of L and first octave of M are
perfect together.. they should have no beating between them..
play some fifths and other combinations too
this is your reference octave
(if it has a tone chamber, these would be the reeds in the chamber)
then finish tuning the L and M reeds, constantly referencing/comparing
the other reeds you are tuning to that perfect reference octave
play the heck out of the base L and M reeds solo and in combination
chords fifths augmented listen for stray beats and tune them into submission
once you have the CORE reedsets tuned perfectly...
then, decide what you want the accordion flavor to be
French, Italian, German, Scottish, Jazz ?
do you want to have your primary musette be gentle enough
for full chords, for sweet French songs and sweeping
orchestral Waltz music ? then be conservative with the M+ reeds
i would tune the first/lowest octave of M+ out of the accordion
to a "formula" based on your preference, then put it back in and
play the M and M+ reeds together and decide if that is what you want,
and note what you need to do/adjust so the "beating" is about the same
as you go up that first octave
then do the rest of the M+ reeds, hopefully what you learned doing
the first octave gives you clues that makes things easier
once you have the M and M+ reeds sounding nicely tuned,
and L M M+ together sounding great, THEN you decide how
low you want to go with the M- and how wet you want it to turn out
i would tune it a hair lower at first, cuz you can always make
it even lower, but it is a bear to make it higher again if you mess up badly
if you do not have enough flexibility in the preset shifts to
give you all isolation and combinations, just take the grill off,
remove the shifts, and then you can open and close each reedset
with your fingers on the little pivots the shift arms were connected to
that is how i would approach it
