It's an ad for the car battery used to run the setup. Next: "Are Friends Electric" performed on refrigerators with iffy compressors. [Die Hard]
Update: Adam Sadowsky, president of Synn Labs, writes in to explain how they created the "corgan":
We're the same folks who built the Rube Goldberg Machine for OK Go's music video for "This Too Shall Pass". In fact, both shared the same director, the amazing James Frost of Zoo Films who brought us in to build the "corgan" for them.
FWIW, we installed new horns in each car that we'd tuned to honk the correct note for their placement on the keyboard. This proved to be easier than modifying the stock horns already on the cars – not to mention easier to return to "normal" before returning them to the various owners!