Harmonix initially tried to release the patch back in December, but was blocked by Guitar Hero owner Activision. Activision later claimed that it should be "compensated for the use of our technology," though the Xbox 360 edition of Rock Band was already compatible with the system's Guitar Hero instruments.
That stance changed earlier this year, as Harmonix, Activision and publisher Konami all promised that this fall's trio of music games--Rock Band 2, Guitar Hero World Tour, Rock Revolution--would all function with each others' guitars, drums and microphones.
In addition to guitar compatibility, the September 11 patch for Rock Band PS3 will add the disc export feature, which allows most of the game's songs to be played in the forthcoming Rock Band 2 for $5, and a fix for the only-broken-on-PS3 PAX Pack.
A fixed version of the PAX DLC should be up in the PlayStation Store before Thursday and will be free for those who already purchased it, community manager Sean Baptiste wrote on the game's official board, but the patch will rectify the issue for the lazy.