Not a physicist. I think, if you get a standing wave going, say on a drum surface, and slowly change the frequency slightly up or down, a piece of rice sitting

Not a physicist. I think, if you get a standing wave going, say on a drum surface, and slowly change the frequency slightly up or down, a piece of rice sitting on the drum can be moved around. The rice will tend to settle between nodes. If you have significant enough energy, the interference patterns can 'drive' an object. Apparently this can be done in midair, with enough energy to break gravity. And can be entirely controlled. Sweet. Edit, spelling.