Because there really is an “app for that,” here’s an app — just 99 cents! — that makes music from bar codes.
It’s called Barcodas, and what you do is scan any bar code with your iPhone 4 or 3GS or iPad 2, and it reads the bars and makes musical notes as… well, look:
Different width bars correspond to different notes, and you can share the “music” on Facebook.
I would guess that this would be amusing for about five minutes, but I’m sure someone out there will figure out some cool way to compose a symphony or something with it. If you want it, the iTunes link is here.