Matthew asks why it is not possible to use the square punches to cut
music for a keyless organ.

The standard pitch for most organs is 3.5mm, whether they are keyed or
keyless.  There are some, particularly German, organs that deviate from
this and also some that use different transport speeds for the card.
Interestingly, the original pitch for Gavioli organs was 3.49mm.

The square ended punch for keyed music has a width of 4mm; so it is
wider than the pitch.  This is for reasons of more reliable playing in
the event of slight mis-tracking of the card either when playing or
when being punched.  A keyed book can mis-track substantially before a
wrong note is played due to the entire key having to rise to play.  If
a keyless book were to be punched with 4mm wide holes it would very
quickly play the wrong notes on mis-tracking, owing to the edge of the
slot in the keyframe being uncovered by the wider slot in the card.

Another reason for using round holes in keyless music is due to the key
length issue.  The keyframe key has a length of around 2mm when raised,
so this means a 2mm long slot  in the card will not play anything.
Ideally, card music slots must be 2mm longer than the required length
of the note.  It is unusual for any slot to be shorter than 5mm.  In a
keyless organ, with its prompt action, even a single 3.2mm hole will
play; so for this reason, a keyless punch traditionally uses a circular
die.

For more details about German organ scales and keyframe dimensions, see
"Waldkirch Street and Fairground Organs," by Herbert Jüttemann, in the
English translation by Andrew Pilmer, which is, I believe, still
available from Andrew.

Nicholas Simons,
GB