“Who’s that?” A$AP Rocky asks when the Dirty Projectors begin their set and start emitting their pitch-perfect vocal harmonies at the 2012 Pitchfork Music Festival. When informed of the Brooklyn indie rock group’s handle, Rocky stands up to get a better view of the group. When he sits back down a minute later, he asks an ASAP Mob member to write the name ‘Dirty Projectors’ down and asks, “What do they make? Reggae?”

So it goes at Chicago’s Pitchfork Music Festival, where genres awkwardly bump against each other and tastemaker-approved artists unwittingly discover each other’s mass appeal. An hour before speaking with Billboard.com, Rocky had wrapped up an unrelenting, brilliantly vacuous set alongside his A$AP Mob cohorts, stomping through “LiveLoveA$AP” cuts while threatening the audience to put their hands up. When the rain started and quickly intensified, no one in the crowd moved a muscle; instead, they bounced along with the bass of “Hands on the Wheel” and supported crowd-surfers during “Wassup.”

For Rocky, a 23-year-old Harlem native who inked a deal with Polo Grounds/RCA late last year, performing at 5:30 PM to a crowd of indie rock fans is nothing new; in fact, it’s sometimes preferred. “I got supporters from all demographics,” says the rapper. “There are people that don’t fuck with rap but fuck with A$AP, just because I give them a feeling that they can’t explain. I’m used to this happening – even when it’s not at one of these festivals, my crowd is real diverse. If you’ve ever been to one of my shows, you’d be like, ‘What the fuck did I just step into?'”

“LongLiveA$AP,” Rocky’s major label debut, is slated for a Sept. 11 release date, but the MC says that a record featuring his entire A$AP Mob hip-hop crew — which includes A$AP Twelvy, A$AP Yams and A$AP Ferg, among others — will be out before that. Rocky won’t give an exact date, but says that fans will have it “in two weeks.” A$AP Ferg chimes in that, on the Mob album, “Everybody has their own unique sound. Rocky set the tone.”

One week after Friday’s performance at Pitchfork Fest, A$AP Rocky will make his network TV debut on “Late Night with Jimmy Fallon,” with a song scheduled for Friday, July 20. But when asked about a radio single from “LongLiveA$AP” that could provide a strong hook on “Fallon,” Rocky insists that he’s not going through the standard tropes of a major label artist.

“I’d put out some whack, slow shit, straight up. I’ll just put out a song saying nothing – call me Pootie Tang,” Rocky says with a laugh. “Putting out that motherfucking tastemaker music that we do, we change the sound of mainstream. The mainstream isn’t gonna be that bullshit that you hear on the radio all day. The mainstream’s gonna be that A$AP — we’re gonna change the whole world with this shit. I have a dream! I’m the trill Martin Luther King, straight up.” –Billboard