This is an interesting sound project by Diego Stocco.

Notes from the sand music maker:

I had some sandbags in the backyard that I used in November during a rainy day. I was moving them to a different spot when I heard the noise of the sand. I thought that maybe I could try a new sound design technique so I bought some piezo film transducers and started to experiment with them.

Link via Scene 360 Illusion