I know that the restoring department of the Museum van Speelklok
tot Pierement in Utrecht have recently found a good way of making
MIDI files from organ barrels, which they put into good use when
they managed to make a copy of the cylinder of one of the
Niemecz-Haydn organs, now in their collection. There is lots of
software to convert MIDI-files into written music. The E-mail address
is <email@example.com>. I wish your Austrian friend success!
Hans van Oost, Netherlands