This may duplicate information you already have, but _The
Fabulous Phonograph, 1877-1977_, by Roland Gelatt (New York:
Collier Books, 1977), contains the following on Page 77:

        A reporter from _The Phonoscope_ visited the studio
        [Gianni Bettini's Fifth Avenue studio] in 1896 and
        came away dazzled by the cylinders he had heard:

             The collection...is unequaled anywhere...
             The next cylinder was one labeled "Melba,"
             which was truly wonderful; the phonograph
             reproducing her wonderful voice in a mar-
             velous manner, especially on the high notes
             which soared away above the staff and were
             rich and clear. Mark Twain interrupted the
             singer with a few remarks on the experience
             he had had in trying to make practical use
             of the instrument. The humorist is now on
             his lecturing tour around the world and the
             record he made in the phonograph was taken
             in December 1893...

The book goes on to say, "Considering Bettini's prices and
the small scale on which he operated, it is doubtful whether
he sold more than a few hundred copies of any one recording.
In no other way can the fact be explained that today Bettini
cylinders are even rarer than Gutenberg Bibles or Shake-
speare quartos. A group of them was discovered in 1945 in
Mexico City--none, unfortunately, by singers of eminent
stature--and sold to a collector in Boston. I know of no
other authenticated Bettini cylinders in existence;
Bettini's own collection of 'originals' was stored in a
French warehouse in 1914 and destroyed by bombing during
World War II."

Besr regards,

Mary Leah Christmas