Versatility has not served Michelle Shocked well. Dropped by Mercury Records, against which she recently began legal action, the genre-hopping Texas singer/songwriter, who went from big-band chanteuse on 1989’s Captain Swing to roots revivalist on 1991’s Arkansas Traveler, was forced to hawk her latest album, last year’s self-produced Kind Hearted Woman, at live shows. Tonight, the avowedly political Shocked performs a benefit for the grass-roots activist group 20/20 Vision, whose members commit a modest 20 minutes a month to letter-writing campaigns aimed at bringing about social change. At 10 p.m. at the 9:30 Club, 930 F St. NW. $20. (202) 393-0930. (Nicole Arthur)