Jack,  Have your postmistress read the definition of Media Mail in the
USPS Domestic Mail Manual.  Sound recordings in all formats, regardless
of the material on which they are captured, qualify as Media Mail.

Phonograph records, whether shellac or vinyl or metal, qualify.  Music
rolls, whether on paper or metal (as the Tel-Electric uses) or acetate,
qualify.  I don't see why musical box discs would not qualify.

Here is what section 473.2.2.e of the Domestic Mail Manual says about
sound recordings: "Sound recordings, including incidental announcements
of recordings and guides or scripts prepared solely for use with such
recordings. Video recordings and player piano rolls are classified as
sound recordings."

I believe that Q.R.S. or Play-Rite or Ray Siou had to get a ruling from
the Postmaster General of the United States to clarify the issue with
piano rolls, which incidentally include music rolls of all sorts.  You
may need to follow the same route or at least discuss your intent to do
so with your local postmistress.

Q.R.S. used to sell a piano roll rack (maybe it still does), but would
ship it by USPS mail only if you bought piano rolls with it.  It took
me a long time to figure out why.  If the rack is used as a shipping
"container" for the piano rolls, the whole thing is eligible for Media
Mail.  Without the rolls, the rack has to be shipped by private
carrier, like UPS.

By the way, the USPS's earlier name for Media Mail was "Book Rate."
The nice thing about these rates is not only that the cost per pound
is rather low, but the cost does not depend on distance, unlike Parcel
Post (regular 4th class) service.  For that reason, it may be cheaper
to use regular 4th class to ship a music roll across town; but to ship
it across the country, Media Mail can't be beat.

Matthew Caulfield
Irondequoit, New York