Of all the sounds now vanished from the heart of old downtown Los Angeles — the songs of the Tongva , the whistles of steam locomotives, the clanging of streetcars — there’s one you’d never have expected: the Rebel Yell. The battle cry of the Confederacy resounded a long way from its home, but throughout the Civil War, you could hear it in secessionist hangouts like the old Bella Union Hotel. The yell usually went along with hollering and arguing, and maybe the bibulous singing of “We’ll Hang Abe Lincoln To A Tree.” That was the Confederates’ poor rejoinder to the Yankees’ insult song about the Confederate president, “We’ll Hang Jeff Davis From a Sour Apple Tree.” (Poor, because the meter doesn’t scan, and who hangs anyone to a tree, anyway?) Like the song, the Confederacy was a failure. But here — here, in now politically azure-blue L.A. — sympathy for the South was muscular and, as far as the U.S. government was concerned, a potential menace. Think of Jets and Sharks decked out in buckskins or Yankee blue, ambling down our grubby streets, swapping