Endowed with a voice caught pleasingly between the sweetness of a Bobby "Blue" Bland and the grit of traditional blues shouters, Johnny Christian delivers both blues and steamy chitlins-circuit soul with conviction, enthusiasm, and a savory blend of slickness and blues honesty. One of Christian's main assets is his band, the Chicago Playboys. Saxophonist Kareem boots out funky roadhouse phrases with just a hint of Dexter Gordon-like sophistication, and the keyboardist--a woman who goes by the name of Coffee--doubles as a powerful vocalist in the great mid-60s, Aretha Franklin gospel-blues tradition. As if this weren't enough, Christian is sometimes joined by vocalist Shirley Johnson, whose amp-shattering alto combines a similar gospel fire with smoldering sexuality. Her slow-grinding, torchy version of "You Can Have My Husband (But Please Don't Mess With My Man)" could melt the ice off Lake Michigan in mid-January. Tonight and Saturday, New Checkerboard Lounge, 423 E. 43rd, 624-3240; Sunday, 2:30 PM, Michelle's, 5453 W. Madison, 261-9440.