You may never have asked a musical question along the lines of, "How could anyone possibly turn a hoary burlesque-era tune like 'Ma, He's Making Eyes at Me' into a blues?" Nonetheless, you'll find the answer on jazz singer Etta Jones's new album Reverse the Charges (on Muse). In fact, I'd bet you could plug virtually any song title into that question, from "Rocky Mountain High" to the theme from The Flintstones, without deterring Jones: on any path between two tones, her voice seems to naturally gravitate to the blue notes in between--like a kid drawn to every mud puddle on his way home--and she couldn't keep the rhythmic jump out of her style for all the tea in China. Everyone argues about what makes a jazz singer, and Jones's clear debt to other idioms makes her suspect in some camps. But if you banish her from the jazz shelves, you'll also have to remove classic performances from the likes of Louis Armstrong, Charlie Parker, and Lester Young--all of whom dipped pretty deep into the blues bag. Joining Jones in Chicago is her longtime musical director, the ballsy, sweet-toned tenor saxist Houston Person; he also straddles the boundaries of jazz, blues, and soul, ensuring that, for five days at least, the south side's border will be shifted considerably north. Tuesday through next Sunday, December 13, Joe Segal's Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4846.