Young Playwrights Inc. launches its 20th anniversary season with Show & Tell, a dazzling evening of songs, shmooze, and chat with some of the leading figures in American theater. Stephen Sondheim, Alfred Uhry, Wendy Wasserstein, Lynn Ahrens, Stephen Flaherty, Richard Maltby Jr., David Shire, Carol Hall and Sheldon Harnick are on hand. The theme of the evening is to perform songs cut from or added to well-known American musicals at the eleventh hour.