Your friend should contact the Museum van Speelklok tot Pierement in
Utrecht.  They have done just that to produce a book of sheet music
from the barrels of several of the recent "Royal Music Machines"
exhibition pieces.  Their web site is http://www.museumspeelklok.nl/
I believe they used an operator turning the barrel against a key frame
pattern and then manually inputting into a computer program (but that
is only an educated guess).

John Farmer, UK
Archivist, MBSGB