Why Rock Band 4 on Xbox One requires a legacy game controller adapter?

Xbox One uses a different wireless communication system than Xbox 360. Because of this, Xbox 360 wireless controllers and accessories are not directly compatible with Xbox One.

The Legacy Game Controller Adapter allows Xbox One to recognize and use most legacy wireless Rock Band controllers.

This adapter enables backward compatibility so you can continue using supported Xbox 360 instruments with Rock Band 4.

Note: Only supported wireless legacy controllers will work with the adapter.