"I got to know this city over the past seven or eight years," Steve Earle told his Rams Head audience Tuesday night. "I know all about lake trout now. I learned about Baltimore from some guys who grew up here and loved the city enough to turn it into some of the greatest art America has ever produced: The Wire."Earle looked very much like Walon, the character he played on The Wire: a streak of white running through his Old Testament beard, the sleeves of his snap-button denim shirt rolled up. As Earle acknowledged, it didn't require much acting for him to play a garrulous, recovering addict from Texas, nor did it take much acting for him to play Harley, the garrulous street singer from Texas in David Simon's new show, Treme.Earle had opened his solo-acoustic show at the Rams Head with the theme song from The Wire: Tom Waits' "Way Down in the Hole." He taught the audience the "In the hole, in the hole" refrain, and used that impromptu choir as a counterpoint to his vocal and harmonica solo. His fourth song of the night also had a Maryland connection: "Taneytown" is a story of parental neglect, racism ,and a bloody Randall knife set in a small Carroll County town.It was an up-and-down evening. Many of the uptempo numbers, even songs as strong as "Copperhead Road" and "Someday," suffered from Earle's lackluster guitar rhythm. But the finger-picking ballads were often spectacular. When he got those pretty guitar arpeggios going, he seemed to relax into his still handsome tenor and brought out all the melancholia of songs such as "Goodbye," "My Old Friend the Blues," "Now She's Gone," and his mentor Townes Van Zandt's "Pancho & Lefty." He usually topped them off with an even sadder harmonica solo.Treme is set in the winter and spring after the levees failed when Hurricane Katrina sideswiped New Orleans. Simon asked Earle to write a song that his character Harley might have written that spring and to play it on the final episode. Earle reprised it at the Rams Head, and "This City Won't Drown" sounded like a rallying anthem as strong and persuasive as his encore version of "Christmas in Washington."