John Page, UK, wrote in 011128 MMDigest, "Dutch Street Organs by
Carl Frei":

> Otherwise it can be caused by slack keyframe drive belts.  The
> majority of Dutch street organs are fitted with round-section leather
> belts running in round-grooved pulleys, not exactly conducive to a
> sure grip.  Lifting the "bridge", even momentarily may cause the
> registers to operate in a random fashion, thus ruining the music.

Thank you, John, for a nice extension to my reply of yesterday.  Yep,
I forgot to mention the leather drive belts.  You can also fix those
belts easily using these solutions:

1.  shorten the belt, thus tightening it more, or
2.  install a tightening mechanism.

To solution 2: This might be an extra adjustable roller which the belt
has to run around, while the adjustment either could be a fixed
adjustment with a screw, or (as I've also already seen, but not really
liked) a permanent self-adjusting mechanism with a spring pulling the
roller up, or with a weight pulling the roller down.

A "final" solution would be to replace this belt mechanism with a chain
mechanism as found in your bicycle.  :-)  This wouldn't be traditional,
though.

About lifting the "bridge" (latch):  The problem John Page mentions
here exists in most Dutch street organs, but not in all organs playing
book music.  If you don't have any registers, or if all your registers
always play at once, or if your registers are switched manually: don't
worry about it!  :-)

If you have register key controls in your books, however, then you need
a tiny little bit more "know-how":

1. Check where the key lines of your registers are positioned in the
book.  (If you are an organ operator and/or know about "reading" your
book-music, this is the most easiest part, as these are the holes that
don't make any sense as of notes :-)

2. Open the latch, fix the problem you had with your book, then check
for the nearest location of a register hole in the book (back or forth
in the book) and place this part right in front of or in middle of your
keys in the table, then close the latch.  If you do so, you can keep
playing without a "gap" of a missing register.

However, if you do not know how, usually the instrument will not sound
bad, just the music will be partly missing, e.g., playing accompaniment
with bass, but no melody.  It will fix itself with the next punched
register hole.

greetings by(e) InK - Ingmar Krause