Since Harmonix first announced it was bringing the Rock Band franchise to a new generation of consoles, there have been persistent questions about how the new games would support guitar and drum controllers designed for older systems. The answer to those questions comes with a price for Xbox gamers who will have to pay $20 extra if they want to use their old Xbox 360 instruments on the Xbox One.

The extra cost is to cover the inclusion of a "Legacy Game Controller Adapter," which preorder listings show coming packaged with the standalone Xbox One version of the game for $80. The $60 PlayStation 4 edition has no such adapter, since the previous PlayStation 3 instruments already required a USB dongle to support wireless play (that dongle will still be required to use old instruments on the PS4, but new PS4-specific instruments will sync directly via bluetooth).

While the price difference is a bit galling for players in Microsoft's ecosystem, it's still a much better deal than shelling out $250 for the "Band-in-a-Box" package, which includes new drum, guitar, and microphone controllers, or $120 for a package that includes a new wireless guitar controller (those prices are the same for the PS4 version as well). Activision's upcoming Guitar Hero Live won't work with old guitar controllers at all, requiring users to pay $100 for the game and a new controller with a six-button, two-row configuration.

In March, Harmonix product manager Daniel Sussman told Ars Technica that getting cross-generation compatibility for Xbox One controllers was a particular challenge for the developers. "[Microsoft] has a team working on it, but there’s an archaeological dig that needs to take place, what the 360 protocols were," he said. "Everyone at Xbox moved on to Xbox One. I mean, where would you even buy some of those chips now?"

Mad Catz, which worked on the Xbox controller adapter and new Rock Band 4 controllers, had similar thoughts when talking to Ars today. "Bringing backward compatibility forward from previous generation consoles was actually a huge technical challenge, one I might add that has never been undertaken before," Mad Catz spokesman Alex Verrey said. "Most game developers wouldn't dream on such an undertaking but Harmonix and Mad Catz thought it the right thing to do for the community. Xbox 360 architecture is actually very different indeed from Xbox One, with peripherals communicating with the console in a very different way. In order to create a 'bridging' device, we had to work closely with Microsoft as well as Harmonix and Mad Catz engineers to ensure that latency would not be a concern and that gamers could mix-and-match old and new hardware."

Harmonix also announced results of its internal Rock Band 4 compatibility testing for a variety of guitar and drum controllers released alongside various Rock Band and Guitar Hero games in the last console generation. You can check if your specific controller is supported using the chart below. Rock Band 4 is due for release on October 6.