There's an iPhone app, Replay, that does something similar: automatic music/video tagging to build a video "counterpoint". Of course it's more limited, as it's

There's an iPhone app, Replay, that does something similar: automatic music/video tagging to build a video "counterpoint". Of course it's more limited, as it's intended for general public, but the Epic theme is quite convincing. Disclaimer: I am CTO @ Stupeflix.