I just finished building a little monkey automaton to go with my
calliope.  He beats a toy drum more or less in time to the music.

I used the innards from an old "dancing beer can" from the 'eighties
that one of our kids had given us as a gag present.  This contained
a sensor that caused the beer can to gyrate when a loud noise occurred.

It works pretty good as the mechanism for the monkey, as well as being
easy to build and cheap.  There is a picture of him as well as a video
clip, on my home page, under "Calliope":
http://members.cox.net/rpartos

Dick Partos