EUGENE - "There will be only percussion in the orchestra for the first act," Tan Dun said, "all women, wearing no clothes." The second act orchestration is for various paper instruments, the third for ceramics only. The women's chorus will be in a tea bath. I didn't bother to ask what they'll wear. Between last night's US premiere of "Water Passion" at the Oregon Bach Festival and tomorrow's concert of three orchestral works, Tan paused long enough this afternoon for an interview about the opera he just finished. "Tea" will premiere in Tokyo's Santori Hall in October, continue to the co-producing Dutch National Opera in Amsterdam next January, to Shanghai, and then - if Tan's track record remains intact - all over the place. The work, four years in the making, uses Tan's own libretto, about the "invention or discovery of tea." It will be, he said with a twinkle in his eye, "sensual, erotic, spiritual." The protagonist is a Japanese prince, travelling to China in the 8th century to find the Book of Tea. He will be involved in a love story, but - as far as I understood - not with the percussionists. Who will direct - Robert Wilson? No, said Tan, "the next generation." Among the many other works the much-commissioned Tan is involved with: an opera for Placido Domingo and the Met, to premiere in 2005, and to be presented also at the Beijing Olympics in 2008. Won't Domingo be too old by then to sing the title role? He'll be only as old then, Tan replied, as Pavarotti is now. I dropped the topic. Tan hasn't decided on the subject yet, but there are two strong possibilities: the story of Jewish refugees in Shanghai in the '40s or an opera about dreams and reality, featuring Freud and Lao Tzu. Fully dressed, most likely. Janos Gereben/SF In Oregon, to July 8 [log in to unmask]