In 1987, aspiring rapper Timothy Parker met DJ Xavier Mosley in economics class at Kennedy High School in Sacramento. Parker became MC Gift of Gab and Mosley became DJ Chief XCel and together they formed Blackalicious. In the two decades since that time, the duo has become one of the most beloved groups in hip hop, praised for bringing intelligence back to a music form sometimes panned for its shallowness. Rolling Stone called Gift of Gab a "phenomenal lyricist who could battle any of today's multi-platinum-selling MCs," and the Village Voice called XCel "technically miraculous." Gift of Gab, Mr. Lif and Chali 2na (Jurassic 5) will play Monday at Harlow's in a show hosted by fellow rappe