‘It’s just like being in school!” says musical-theater sensation Audra McDonald of rehearsals for her impending debut sans music in Lincoln Center Theater’s production of Henry IV, which starts previews on October 28. “The thing with these sprawling Shakespearean pieces is there is a huge cast and lots of downtime for everybody,” says a relieved McDonald, who in the past has carried shows like Master Class and Carousel on her stylish shoulders (she won Tonys for both). “Women didn’t tend to do any of the battles. So there’s lots of time to observe and learn from the masters like Kevin Kline (Falstaff) and Ethan Hawke (Hotspur).” In the play, directed by Jack O’Brien, who also did a little show called Hairspray, McDonald is Hotspur’s wife, Lady Percy. “She’s very unconventional in that she considers herself the equal of her husband, with whom she has a very sexy relationship,” she says. “It’s quite exhilarating to play someone who speaks her mind!” Cozying up to Ethan Hawke must not be too painful, either. “Well,” she says, blushing slightly, “what do you think?”