Given it's a cartridge, there's more than just audio here. Each track is accompanied by some pixellated visuals -- a music video of sorts -- and there seems to be some kind of mini game too (pause the video below at 1:32). Unfortunately, this unusual music release is only planned for Japan. It'll be available through Amazon for 3,800 yen (roughly $30) from January 31st and only "several thousand copies" are being made, according to the Wall Street Journal. But if it's popular, who knows -- maybe we'll get a NES version too...