Sound Soup allows people to collaborate in additive synthesis using the browser on their device.
Inspired by Daphne Oram's sound recipes, this web page generates a random frequency from a selection of a fundamental and it's first 13 harmonics
Press on the ingredient (the veggies) to hear the tone generated as a single sine wave. Others nearby can join you through pressing on their ingredient, adding their tone to the mix.
This hack works on a principle of a single simple interaction that allows users to "interact through" (as opposed "to interacting with") their device in a collaborative way of generating sounds.