Vic Chesnutt and Kristin Hersh, with the Willard Grant Conspiracy, Tuesday, May 23, at the Fox Theatre, appear on a double bill they've dubbed "In Their Own Worlds." It's an apt title considering Chesnutt and Hersh are songwriters who seem tapped into a creative dimension invisible to the normal, naked eye -- observers of a world artfully distorted by uniquely individual lenses. Chesnutt's latest recording, The Salesman and Bernadette, found the sardonic, wheelchair-bound Georgia boy mating alternatively simple and grotesque imagery with acoustic guitar balladry and full-blown quasi-gospel; on the current tour, however, he plans to focus on material more conducive to a solo live performance and songs from his forthcoming and intriguingly titled Roses for the Butt of All Our Merriment. And though Hersh's longtime band, Throwing Muses, hovers primarily in the inactive zone these days, she remains a prolific solo songstress: Last year's Sky Motel was her most inspired showing in years -- a reminder that she sometimes seems capable of channeling ghosts through her songs. In their own worlds, indeed.