Why does Rock Band 4 for Xbox One need a Legacy Game Controller Adapter?

With Xbox One, Microsoft updated the wireless connectivity security protocol that exists between wireless controllers and the receiver on the console. Because of this, wireless Xbox 360 controllers and accessories aren’t natively compatible with the Xbox One. In order to support the vast amount of cool Xbox 360 wireless Rock Band controllers already out there, Mad Catz and Harmonix worked together to design the Legacy Game Controller Adapter for Xbox One that enables backwards compatibility for most legacy wireless Rock Band controllers.