Notable Events:
- Naughty By Nature's Naughty by Nature is released on 9/3/1991 
- Nice & Smooth's Ain't a Damn Thing Changed is released on 9/3/1991 
- W.C. and the Maad Circle Ain't a Damn Thing Changed is released on 9/17/1991
- A Tribe Called Quest's The Low End Theory is released on 9/21/1991

1991: The year the Soviet Union was disintegrating. That September, the United States recognized the independence of former republic states Estonia, Latvia, and Lithuania. Hip-hop, too, was continuing to break apart and evolve, as a string of sophomore records found the late-80's new school rookies evolving. New Jersey made its stamp on the industry as Naughty By Nature shot from obscurity. Recently renamed—the group first appeared as The New Style in 1989 for one unsuccessful LP—Treach, Vinnie, and Kay Gee had released lead single "O.P.P." only days earlier, and the song would soon rocket to No. 6 on the Billboard charts. After the self-titled album was released, it would only take until February 1992 to reach platinum sales off the surprise smash.

Meanwhile, Def Jam had begun to splinter, much like the once-mighty Baltic states. One of Rush Associated Labels' few successes, Nice & Smooth released their second LP, Ain't a Damn Thing Changed, and found a surprise minor hit with the Tracy Chapman-sampling "Sometimes I Rhyme Slow." In one of the strangest coincidences in rap history, West Coast rapper W.C. and his crew the Maad Circle (which included future star Coolio) would release a certified rap classic similarly titled Ain't a Damn Thang Changed—in this case, the group's debut. Apparently, no matter where you were, the streets were unchanged—even if hip-hop would never be the same.

Of course, one of the greatest sophomore records in rap history was also released in September 1991, when A Tribe Called Quest dropped their impeccable Low End Theory. A maturation of the group's playful debut, it maintained a lighthearted style, but found the trio's sound developing into a distinct aesthetic of its own, exploring new sampling sources and a fully developed chemistry between MC's Phife and Q-Tip. —David Drake