To anyone else, the 2.6-mile Cascade railway tunnel under Stevens Pass, finished in 1900 and abandoned in 1929, might be merely a historical relic. But for Seattle percussionist Paul Kikuchi, it's served as a recording studio. Fascinated by resonance and the interaction of music and its surroundings, he's also played in an empty cistern—a two-million-gallon tank with a 45-second reverb time—near Fort Worden. But his next project will be more accessible to the public. In fact, accessibility is part of the point for his percussion happening next Tuesday at Union Station (sponsored by 4Culture and Sound Transit). To Kikuchi, the sounds of the cavernous Great Hall are compelling on their own: "Before I even played in there," he says, "I would just go sit in there, and somebody walking by with their keys jangling, or the changing of the trash cans in there, is just amazing, it's thunderous." So Kikuchi's lunch-hour performance won't be a sit-and-watch-me recital, but simply a part of everything already going on, a way to encourage people to pay attention to the sounds that happen in Union Station all the time. He'll play primarily vibraphone, but also bring a collection of his invented instruments, made from materials like found glass goblets and scrap metal. After his solo set, Kikuchi will be joined by two other sonic explorers, Stuart Dempster and Susie Kozawa. For a September 18 performance, he's planning to bring even more players, with ensembles scattered around the station.