Every once in a while, the legendary Vincent Davis emerges from his South Side digs to remind people that he's one of free jazz's best drummers. He's had various regular gigs around the city over the years — most recently, a long stint at the Old Velvet Lounge with Art Ensemble bass player Malachi Favors. Davis now brings his own trio to the Velvet Lounge for several nights this July, starting on Thursday with Ed Wilkerson on reeds and Harrison Bankhead on bass.