In Chicago, there seems to be a chronic need to collaborate continuously, with as many different people as possible. Rob Mazurek and Chad Taylor, mainstays of the various Chicago Underground configurations (Duo, Trio, Orchestra), get around as much as anyone, but they really don’t need anybody but each other. The Duo’s latest ethereal rhythm ‘n’ bloops fest, Axis and Alignment, is a disc as rich in melody as it is in texture and groove. Mazurek is primarily a cornetist with a bop background, but over the past decade, as his tastes have grown to include modern classical and electronica, he has started to contribute piano and electronics to Chicago Underground’s releases. (Don’t be surprised if he soon adds South American folk music to his repertoire: Mazurek moved there recently with his Brazilian wife.) Percussionist Taylor doesn’t team with Mazurek just to add polyrhythms; he co-writes tunes and plays guitar and vibes. They have a symbiotic relationship, and whatever they’ve done apart hasn’t approached the drifty beauty, dense but funky rhythms, and overall sense of completeness that the Chicago Underground permutations achieve. If New York is the center of the jazz world, then Chicago, and its Duo/Trio/Orchestra, is what provides the atmosphere. The Chicago Underground Duo plays at 9:30 p.m. Friday, April 12, at the Black Cat’s Backstage, 1811 14th St. NW. $8. (202) 667-7960. (Christopher Porter)