As a solo rapper, Big Boi has been pushing steadily against the old preconception that he was the less-daring half of Outkast. On all three of his solo albums—Speakerboxxx counts— he happily explored his quirks, establishing himself as someone more than just Andre 3000's more stolid counterpart. With Sir Lucious Left Foot: The Son of Chico Dusty, he pulled off an incredible, boisterously funky reintroduction. Vicious Lies and Dangerous Rumors paired him with Wavves, Little Dragon and Phantogram among others, and if the results were mixed, it was further evidence of Antwan Patton's voracious ear.

Vicious Lies paved the way for this full Phantogram collaboration. The indie-pop duo featured on three of the songs on Vicious, but on Big Grams they hit a bit more of a stride. This isn't a Big Boi-on-Phantogram beats project, and Phantogram's Sarah Barthel is nearly as central as the OutKast rapper as a lead vocalist. The two trade spots as lead vocalists playfully and Barthel's hooks are integral throughout. Barthel tries some rapping, and the results aren't actively embarrassing.

"Run for Your Life", the lead track, is sparse and spacey, and the synth sounds lifted from Stevie Wonder's Moog on "Boogie On Reggae Woman". Big Boi's raps aren't deep on Big Grams, but they are captivating: His strategically fluttering drawl, doled out in pitter-patter bursts, is a trademark as recognizable as it is versatile. On "Fell in the Sun" he punches quickly with a staccato: "I whip the yellow Cadillac, I like my seats way back / I bust the sunroof open, beams hit the Braves cap." This track, the lead single, is the obvious standout, and it's here that the collaboration clicks fully. Phantogram's Josh Carter builds up a throbbing wall of synths atop a snappy drum loop, and like elsewhere, horn stabs punctuates: proof, perhaps, that everything Big Boi does deserves a little funk.

"Put It On Her" is one of two tracks on the outing not produced by Carter, and it's certainly the better and more natural of them. (That soulful pump fake of an intro turns out to be a subtle 9th Wonder calling card.) The Skrillex-featuring "Drum Machine", however, sticks out like a sore thumb and bogs down the end of the album. For a record that's so smoothly collaborative elsewhere, "Drum Machine" sounds contrived and clunky. Luckily it is tacked on the end, making it entirely skippable.

The Run the Jewels feature on "Born to Shine" fares better, and not just because of Big Boi's pivotal role in Killer Mike's career. Mike's verse steals the show—"Ric Flair'in' / Long fur coat wearin' / Rolex rockin' / Silk shirt wearin'"—while Big Boi happily takes a backseat. This may be a hallmark of Patton's career: He's continually building up evidence that he doesn't care so much about being the lead as he is interested in being in the middle of something new and different. Given Atlanta's persistent vitality as a hotbed for innovative hip-hop, it's nice to know that one of the city's elder statesmen is off doing his own thing, carving out another little path for himself long after he helped pave the main road.