I had a thought the other week. Every morning on my way to work I see (and hear) a subway performer playing music. Some are quite good, inciting smiles or brief pauses from people walking by. Now imagine these performers had a few jars labeled with different emotions laid out in front of them. Depending on where commuters dropped their coins, the performer would play a song that evoked the respective emotion. Now the money you give to performers no longer goes into a (metaphorical) black box, but has a tangible outcome.