Hi Group,  I am not sure if you would consider this mechanical music.
It is, however, an interesting video.

  http://hgs.co.jp/en/garden-art/xylophone-of-forest.html 

Jack M. Conway
Los Angeles, California, USA

 [ Indeed, it's pre-programmed and powered by gravity!  ;-)
 [ See also
 [   https://www.youtube.com/watch?v=DhIQ2S1gDMM 
 [   https://www.youtube.com/watch?v=VD44QhKuG1U 
 [ -- Robbie