I sometimes wonder if New Orleans has more organ trios than any other city in the world. Since an organ trio usually has no bass player, you have to have a keyboardist who is adept at providing the bass lines with his left hand.  Joe Krown has improved immeasurably since starting his trio with Walter “Wolfman” Washington on guitar and Russell Batiste on drums.  Washington plays all the time with his own band, the Roadmasters, but Batiste has been harder to see outside of this project since the dissolution of PBS.  The Joe Krown Trio plays every Sunday night at the Maple Leaf.  Billy Iuso and the Restless Natives with special guest Ivan Neville on keys open the show tonight at Tipitina’s.