Piccolo vs Mussete

Ive heard both Piccolo an Mussete accordions but what would be the
mechanical difference in them?
Is it the way the reeds or set in the box or is it the actual tunnig
itself?
Also a friend of mine wants to know if his 4 reeded diatonic box can
be Mussete tunned, is this possible?
I know that the piano an cba can be Mussete tuned but Ive never heard
of a diatonic being made this way.
Usually Ive heard of the diatonic boxes being named gfc, ead, adg an
so on....but never Mussete or Piccolo.

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