Dear MMDers, a mechanical engineer friend from Bosnia passed this
along to me, knowing of my interest in "unusual musical instruments."
Although it is not a traditional mechanical organ, it does have
interesting elements for your holiday pleasure.  The link is for
a nice video with music and an interview with the creator:

  http://news.nationalgeographic.com/news/2007/11/071106-organ-video-ap.html
  Organ Played by Lapping Sea

Joe Berman