A minor correction -- I think Bruno Hoffman also plays the "cups".
I have the original VOX record album, from way back in the 1960s,
and while the cover sports a nice engraving of Benjamin Franklin with
his rotating nest of saucers, the inner photo shows Mr. Hoffman with
his instrument, a table with glasses (shaped like beer or wine
glasses).  So he too plays by rubbing fingers around the rims, and
percussing with his fingernails.

Perhaps the German source of recordings does indeed have recordings
of the real Franklin spinning saucers.  I did see such an instrument
in the Vienna museum of musical instruments, next to the Heldenplatz.
I wonder if there's one in Philadelphia?

I heard a street musician play the table of glasses version in
Cambridge (Massachusetts, USA).  He was excellent and I bought his
tape.  He had assembled his instrument from "found" glasses -- no
two look alike.

Some portable electronic keyboards have a sound called "wine glass",
so you could play a MIDI file on "(h)armonica."  In another decade,
MIT may develop a robot capable of playing the glasses.  Meanwhile,
the Franklin version would be much easier to automate, as someone
already mentioned.

Mike Knudsen