Messy Slick unites two giants of underground street rap in California: one from the North (San Francisco’s Messy Marv) and one from the South (San Diego’s Mitchy Slick). Both rappers know how to deliver hood rap with style. Of the two Mitchy is the slightly better lyricist, and he shines on “Diego to Da Bay,” “Hey” and “Tryn to Get a Dolla,” the last of which gives Slick the opportunity to show off his off-kilter but engaging singing skills. Both Marv and Mitchy have respect for the old school tradition, and Messy Slick pursues beats that blend steely aggression and vintage soul to potent effect. “On the One” turns “Strawberry Letter 23” (the syrupy sweet 1977 hit by the Brothers Johnson) into a menacing jingle, while “Cherish a Thug” interpolates a layered, hypnotizing section of Marvin Gaye’s “I Want You.” Best of all is “2nd Letter,” which loops a grubby, groaning guitar lick, as Marv, Mitchy and San Diego veteran Damu reminiscence on the finer points of Cali gang culture.