The first time I heard some book music played incorrectly on a
Fairground organ was at the 'Expo Steam' in Peterborough, Cambs,
England in 1974.

A very large (89 key?) newly restored organ was attending it's first
rally, the hardened enthusiasts were crowding round and all of the
repertoire was being played for the first time.  Several books did not
have the first or the last page any more so it was not obvious which
way round they should be played.  As a teenager I was the novice and
knew no-one in the grouping, but I had a tape recorder with me.

As the first book played through all those listening were silent and
serious, but nobody knew the tune.  I said "Surely that's the Irish
Washerwoman played backwards and inverted".  I got some dirty looks
from those listening of course.

When the music finished the operator decided to follow my hunch as
there was no other suggestion from anyone else.  To my own surprise
I was actually right and from this cheeky suggestion I started getting
more involved with large instruments as rallies.

14-note organette music made in U.S.A. has to be played back to front
if played on a UK made machine and vice-versa as the reeds were put in
the 'wrong' was round in the two countries.  I have sold more than one
instrument to be told, "The music is 'all a jumble', I want my money
back!"  I then ask what make of music they are playing, suggest they
reverse it, and never hear another complaint.

Angelus 58-note organ rolls or 65-note piano rolls have to be reversed
to play on an Aeolian organ or player piano respectively (and
vice-versa, of course).

I wonder if there are many other instruments with reversible music?

Kevin McElhone, Northampton, England