In addition to announcing 10 new tracks for Rock Band 4, developer Harmonix has now confirmed logistical and pricing details for the music game's standalone PlayStation 4 and Xbox One versions.
The PS4 standalone disc will cost the standard $60, but the Xbox One edition carries an $80 price tag. The price difference comes down to the Xbox One edition requiring a "Legacy Game Controller Adapter." This adapter allows players use their existing Xbox 360 guitars and drum sets; it supports up to four controllers simultaneously, and also works with a variety of third-party instruments.
For PS4, no adapter is required. Legacy Rock Band and third-party guitars and drum sets will work just fine out of the box without any additional hardware.
Harmonix has also published a handy Rock Band 4 instrument compatibility chart to help you determine if those guitars in your closet will work with the new game. Note that the chart is not yet finalized.