Expired. Originally required an export key ($5) and the physical disc to extract files. Rock Band 2
The transition to Rock Band 4 changed the landscape. Instead of a local file transfer, Harmonix worked with Sony and Microsoft to check a player’s purchase history. If the system detected that you had previously purchased the Rock Band 2 export key on your account, those songs would show up as "Free" in the Rock Band 4 music store. Legacy DLC vs. Disc Exports rock band song export key
When the keys were active, the process followed a specific path. For Rock Band 1, players would buy a "Transfer Key," and the game would copy the files directly from the disc to the console's hard drive. For Rock Band 2 and later titles, the process moved to the cloud. Players would enter a unique code found on the back of the manual into the game’s website or console store, which then granted them a digital entitlement to download a "Export Pack" containing those songs. Expired
Export : This was the last major disc export available, though its status has also moved toward expiration in many regions. Instead of a local file transfer, Harmonix worked
Exports are locked to the same platform (e.g., PlayStation 3 to PlayStation 4, or Xbox 360 to Xbox One).