Philippe Rouille has asked a tantalizing question.  Others may know of
a machine which can directly transcribe an unknown pin drum; I prefer
to speculate on how it might be accomplished.

I would first transfer the pin positions to a piece of foil by rolling
the cylinder on the foil.  Then I would scan the foil on a flat-bed
scanner, enhancing the image contrast using tools available in Adobe
Photoshop.

Next, I would process the resulting linear image with the same
techniques used to convert scanned player piano rolls to MIDI
representation.

Finally, I would analyze and edit the resulting MIDI file using a
MIDI sequencer such as Cakewalk.  Programs like Cakewalk have powerful
selection tools which would facilitate separating the multiple tunes on
the drum -- and assigning the proper note scale.  Cakewalk can also
quantize the note timing, removing the small amounts of jitter
introduced in the scanning and conversion process.

Of course, much judgment and musical analysis (and perhaps a bit of
good luck) will still be needed to achieve an accurate transcription.

John D. Rhodes
Vancouver, WA