Broadway’s 2004 fall season is chockablock with revivals and one-person shows. When beautifully produced and performed, they can be a good thing, as seen with the recent stagings of “Assassins,” “Elaine Stritch at Liberty” and “Long Day’s Journey Into Night.” But to be honest, there’s nothing quite like an original play or musical to create anticipation or define a season.This autumn, the only original American drama and musical belong to a new producing org. Leaving the creativity to their scribes, Benjamin Mordecai, Robert G. Bartner, Brian Brolly and Michael A. Jenkins call themselves, quite simply, Producers Four. They are lead producers on the fall season’s only new tuner, “Brooklyn,” by newcomers Mark Schoenfeld and Barri McPherson, and August Wilson’s drama “Gem of the Ocean,” which fills out the new play slot with the British import “Democracy” by Michael Frayn. Although Mordecai has known his three partners for years, the other men hadn’t worked together before he induced them to produce/invest in his 2002 Broadway revival of “Flower Drum Song.” It’s a formidable group with links that cover the legit landscape, from Yale Rep and Long Wharf to Really Useful Co. and Dallas Summer Musicals. Prior to their Broadway commitments, Producers Four invested in the London productions of “Hitchcock Blonde” and “The Woman in White.” Their initial Gotham staging was last season’s “Sixteen Wounded,” which deserved better than it got and closed after only 40 perfs. “Flower Drum Song” aside, all productions to date under the Producers Four banner have been of new works. “We certainly don’t have anything against revivals,” Mordecai says. “In fact, it is likely we’ll be involved with ‘Anything Goes,’ directed by Trevor Nunn,” another import from London’s National Theater and the West End.