The Chicago underground hip-hop scene hit a high point in the early 2000s, largely due to indie label Galapagos4 and its flagship group, Typical Cats. Also on the rise at the time was rapper Robust, whose collaborations with members of the Cats and other G4 artists quickly made him an undergound mainstay. His propensity for complex wordplay and maze-like rhyme scheme was exhibited full force on his 2004 album, Potholes In Our Molecules. Robust plays at Burt’s Tiki Lounge Wednesday night. Also on the bill are Scarub of Living Legends and Mane Rock. The free show begins at 9 p.m. and is 21+.