Yes, Stephen Sondheim really did give the quirky and risque Landless Theatre Company permission to adapt the score of his most commercially successfully musical as a prog-metal piece, leaving the lyrics and Hugh Wheeler’s book intact. What is prog-metal? “Prog-metal is actually a very complex, a very precise, almost classically based metal,” Landless’s Melissa Baughman explained last year when she directed a prog-metal adaptation of Richard Campbell’s Frankenstein. “It’s really intricate [with] emotional highs and lows. It’s not just, ‘Let me rock your face off.’ It’s definitely not heavy all the time.” The Sweeney cast features a bevy of vocalists from local metal and rock bands, led by Nina Osegueda (A Sound of Thunder) as Mrs. Lovett. Landless’s Andrew Baughman, who had the prog-metal idea in the first place, plays the title character. Most of the metal musicians who worked on Frankenstein, now known as the Fleet Street Collective,return for Sweeney. To Aug. 31. Warehouse, 645 New York Ave. NW. Tickets are $25. Call 202-783-3933. Visit landlesstheatre.com.