Robbie, How about setting up the scheme another way:

Main groups -- like "Organs", "Piano's", "Music boxes", "Others" -- and in
each group a couple of sub-groups, like

"restoration:

  techniques
  books
  addresses

and so on.

I know that doing so you will get some redundancy (the MBSI is an example:
they will show up in several sub-groups).

The profit, however, will be that one can easily find what he is looking
for, without the need to read a lot of other subjects.

Let me give you an example: if I want to repair a player piano, and I want
to see what is in the MMD-files, I would have to pay a visit (in your
scheme) to Techniques for Restoration, Music Performance ("How to play"),
History (Manuals from Builders = books), Value of goods, and Mart.

In my scheme one can go directly to the Main group "Player piano's", and
will find all there is gathered at one place.

By the way: a separate group for street-, fair- and dance organs would be
very welcome.

Another subject: a list of museums, where mechanical musical instruments
can be found.

And at last: a list of members.

Bye,

Jan Kijlstra

 [ Those are thoughtful comments; thanks for writing, Jan !
 [ Who else out there has suggestions?  -- Robbie