Clay Instruments

Winter weather has made me slow and unproductive in the studio, still I never stop thinking of clay and the ways this oldest of materials can serve people. An evening jam session featuring a few of my favorite music makers got me thinking about musical instruments.
I've made shakers and whistles in the past, the shakers are pretty high pitched due to the tiny rocks hitting a stone surface. The whistles are ocarinos and can be any pitch based on their size and shape. I wonder what else could be made.
Any suggestions?