Hip-hop wasn’t always so serious.

Before hip-hop became filled with beefing, struggling and self-loathing, it also included a healthy dose of inventive party music, from the Sugar Hill Gang through De La Soul. And Rae Sremmurd is born from that tradition.

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Their debut album last year was filled with energetic, offbeat raps like the leftfield hit “No Flex Zone.” With their follow-up “SremmLife2” (Ear Drummer/Interscope), Mississippi’s Brown brothers, also known as Jxmmi and Swae Lee, have opted to be even zanier, both with their rhymes and the beats from producer (and Miley Cyrus collaborator) Mike Will Made It.

That boldness leads to couplets like “Chinchilla hella furry/Catch me on a yacht eating curry” in the middle of “Came a Long Way,” which is essentially a more serious song about taking stock of their new successful lives. It also leads to the wild opener “Start a Party,” where they attack rhymes with a variety of tempos and vocal ticks, their voices cracking with excitement and cool. On “Swang,” they move from sounding like they’re sucking helium to growling at each other about going to school to be a doctor.

Though “Black Beatles,” which features Gucci Mane, doesn’t immediately remind you of Lennon and McCartney, it does show how Jxmmi and Swae Lee tap into what today’s teens want. It also shows they are both pretty good singers when they want to be, a neat trick they repeat on the lovely “Just Like Us,” which could easily have improved the new Justin Bieber album.

Rae Sremmurd sometimes gets dissed in the hip-hop world as a novelty for daring to enjoy themselves as they rap, but “SremmLife2” actually shows that there’s a whole lot of cleverness behind the seeming simplicity. Who else would turn “All my girls do yoga . . . then get high at night” into a mantra in “Do Yoga”?