Harmonix has been really good about letting people with previous Rock Band games get their music into the newest installments. Each previous game could be put into the next for a nominal fee. This will continue with Rock Band 3 and Rock Band 4. People willing to pay a $15 fee will be able to import their Rock Band 3 on-disc content into the newest game.
An exact date for the import process hasn’t been announced, but Harmonix has revealed a tentative window. A Rock Band 4 update is coming on December 8, and the company is hoping to add the ability to bring Rock Band 3 into the game with that update. You have to be verified to make this deal. Harmonix hasn’t said how exactly that will happen, but people who purchased Rock Band 3 digitally already qualify as it’s tied to their accounts. The company loses the right to sell it digitally on the Xbox Store on October 30, but physical copies will work with this promotion.
For people who are planning to buy Rock Band 3 at the eleventh hour for their Xbox 360 to qualify, know that it’s a $19.99 game. That means it will be about $35 to get the 85 songs from the previous game imported for Xbox One owners looking to take advantage of this promotion.
Source: Harmonix