It's interesting that Lou Donaldson is the son of a minister, because there's definitely a preaching quality about his alto saxophone soloing. Donaldson came up during the bop era and, perhaps inevitably for an altoist of his generation, he began as a Charlie Parker-styled lyricist. By the late 1950s, though, a new, dramatic sense of phrasing and phrase spacing entered his music, a way of playing that sounded much like Gene Ammons' tenor concept transferred to the alto; he even recorded an "Exactly Like You" with startling resemblances to Ammons' hit version--six months before Ammons. Since then, Donaldson's affinity for blues and ballads has made him a longtime favorite among soul-funk-jazz aficionados; in fact, if he's in the right mood he might just sing a happy blues, or play a most perceptive, loving caricature of Parker. Nevertheless, the musician in his personality dominates the entertainer, and he still plays in two different styles, the lyrical and the dramatic, from one song to the next. His old friend Herman Foster's thick, rolling piano provides a flexible and most appropriate setting for Donaldson, so it's good that he's bringing Foster to Chicago with him. 8:30 PM, Tuesday through next Sunday, September 22, Joe Segal's Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4300.