"I'm very lucky this happened. What do you say -- life isn't fair?" That's Caris Corsman philosophizing. Corsman, a native of Bethesda and graduate of Walter Johnson, class of '73, is referring to the fact that her five-week starring stint on Broadway in "Amadeus" is coming to an end.

The story begins with Jane Seymour, who played the part of Constanza Weber, Mozart's wife, here in Washington and on Broadway. She became pregnant and left she show on doctor's orders (or she became bored with the girnd of eight performances a week, as New York gossip has it). Corsman, who had been playing the nonspeaking role of Cahtarine Cavalieri and understudying Jane Seymour, stepped in opposite Ian McKellen and Tim Curry.

But the Broadway law is that "names" sell tickets . . . so Amy Irving, who starred in "The Competition," will take over the role Tuesday -- and Caris Corsman will go back to her silent part.

What about being on Broadway, was she nervous the first time she went on as Constanza? No problem. "Understudies run through the show every two weeks." And besides, the first time she went on, Ian McKellen's understudy was performing for the first time as well. The first time she performed with McKellen was different. "Jane was at the Oscars presenting an award. I felt I had to prove something, you know. It was more than just doing my job." Corsman insists with straightforward pluck it won't be hard to go back to the other part. "You don't expect it [playing Contanza] to be so hard on you. But it is. When I go back to Cahtarina, at least i'll be able to go out late and socialize."