All you have to do to build a buzz is put “and special guests” on your bill. The South by Southwest party-goers will come a’ runnin’, just like they did for The Roots SXSW Jam Session on Saturday night at Brazos Hall.

The last-night-of-SXSW event that promised the “Tonight Show” house band — plus genre-smashing supergroup Big Grams and the aforementioned special guests — attracted a line hours before the 9 p.m. doors-open time, leaving many in the dust once the venue filled to capacity.

#SXSW badge line for the Roots jam goes around the corner and down the street.

— D. Sengupta Stith (@deborific) March 20, 2016

The evening kicked off a little after 10:30 p.m. with a jolly sousaphone leading The Roots into a cover of “Express Yourself.” (Not the Madonna song.)

And about those special guests: Rumors of Ashanti and Naughty By Nature started circulating on Twitter before the jam started, and a lineup that leaked on social media ultimately proved quite accurate.

This is happening at Brazos Hall tonight. The Roots, Big Grams, Too Short, @TalibKweli, Naughty By Nature…

— Covert (@CovertCuriosity) March 20, 2016

But the crowd at Brazos Hall, not all clued in to this, grew restless after a strong start from Black Thought, Questlove and co. gave way to a rotating showcase of somewhat obscure rising talent, with The Roots sitting in as a house band. X Ambassadors squeezed in “Renegade” and a Sam Cooke cover. Bronx rapper Tish Hyman served up major Lauryn Hill vibes and was the valedictorian of the jam’s newbies. Soul singer Marc E. Bassy (performing like a room temperature Robin Thicke) eked out a cover of Radiohead’s “High & Dry,” a sharp-dressed R&B singer named Emily King wisped when she should have wailed.

Then the big guns came out. Veteran emcee Too Short was first and drew comparisons between the longevity of his career and of SXSW itself. Comedian Hannibal Buress emerged to stall for time and to deflate event sponsor Bud Light. As expected and highly anticipated, Big Grams put on the most substantial part of the show. The collaboration between Outkast alum Big Boi and Phantogram’s Josh Carter and Sarah Barthel injected much needed electricity into the room, with “Fell In the Sun” an obvious standout. Barthel and Big Boi’s interplay, awkward as it was, charmed.

And we have Big Grams. My #SXSW dream come true at Roots jam.

— Eric Webb (@webbeditor) March 20, 2016

The most rapturously received moments of the night, though, were the few Outkast tunes that worked their way into the setlist, including a reworked “Ms. Jackson” performed by Big Grams. (Likewise, Phantogram tallied a couple solo joints, like “Fall In Love.”)

Big Boi laying down some "Ms. Jackson" with Phantogram at Roots jam đŸ”„

— Eric Webb (@webbeditor) March 20, 2016

The cameos were rapid-fire quick hits after that, which rankled a bit considering the talent show at the beginning of the night. Rappers Yo Gotti and Talib Kweli made brief appearances. R&B singer Ashanti came out for a very well-received, high energy medley that included a “What’s Luv?” that came just as the night was dragging to the finish line. Naughty By Nature came out for “O.P.P.” and “Hip Hop Hooray,” which obviously reduced the entire audience to a bunch of hands in the air.

Ashanti performs at the Bud Light Factory at Brazos Hall during South by Southwest on Saturday March 19, 2016. (JAY JANNER / AMERICAN-STATESMAN)

As it was in the beginning, so it was in the end. The Roots closed the night with a final jam that really just made one wish that there had been more Roots at the Roots jam. But if you’re going to dedicate about 7 hours of your life from queue to quitting time on one party, seeing Phantogram and Naughty By Nature in one night without leaving the room is quite the feat to boast of. And in a SXSW lacking big star power — save on Drizzy — this jam was certainly an explosive finish.

Treach, left, and Vin Rock of Naughty by Nature perform at the Bud Light Factory at Brazos Hall during South by Southwest on Saturday March 19, 2016. (JAY JANNER / AMERICAN-STATESMAN)