Dear MMD'ers,  British Pathe has put online an enormous amount of film
material they used in their bioscope shorts until 1970.  On the site
http://www.britishpathe.com/ you can download free footage of a lot
of subjects.  When you search on "organ", you can find footage about,
e.g., the Great Gavioli, St. Albans Organ Museum, theatre organs,
barrel organs in the Netherlands, ...

Beware: only the low quality preview is free (and it has a copyright
mark on it throughout the film), but it's still worth a look I think.

Best wishes,

Bjorn Isebaert
Zottegem
Belgium