Hi Jon,  you are asking for a mechanical music instrument museum near
Heidelberg.  It's not so easy to answer your question because there are
at least four interesting museums around that area.  I will give you
some very brief descriptions:

1.  The "Musikautomaten Museum" is a division of the Technik Museum in
the city of Speyer, about 35 km west from Heidelberg.  The exhibition
shows all kinds of mechanical music instruments: small boxes up to huge
orchestrions, dance and street organs.

2.  "Siegfried's Mechanisches Musikkabinett" in the city of Ruedes-
heim on the river Rhine.  It is the very first German collection of
mechanical music instruments and one of the largest in Germany.  It
shows everything from the tiniest box to the giant orchestrions,
including a Bechstein-Welte piano.  Contact

    http://home.t-online.de/home/0672249217/museum.htm

3.  Badisches Landesmuseum, Division "Museum mechanischer Musikinstru-
mente", located in the Castle of Bruchsal in the city of Bruchsal.
Amongst many other beautiful instruments you can see the largest
collection of Black Forest flute clocks (Floetenuhren) which I know
about.  And you can listen to the outstanding mechanical organ which
was designed and built by Bruder for the famous ship Titanic.  Because
the organ could not be finished in time, it survived the Titanic
catastrophe!

4.  The "Elztalmuseum" in Waldkirch, a small city in the Black Forest
where Ignaz Bruder and his descendants lived and worked.  I think it is
a must for all of the interested MMD'ers to visit this historical place
and to watch and listen to the many organs exhibited there, all made
by famous organ makers.

For this very moment that's all the information that might help you.
(I have to go to my living room where a visitor is waiting for me in
order to make a tour with me through my private collection.)

If you would like to get more detailed information, please contact me.
And if you would come to the area of Nuremberg (northern part of
Bavaria) it would be a pleasure for me if you would be interested in
visiting me and my small collection of about 200 historical woodwind
instruments and about 100 mechanical music instruments.

Musically
Christian Greinacher