Just the idea of the Chorus of Westerly's magnificent "A Celebration of Twelfth Night" is deliciously overwhelming. You've got the chorus' mellifluous 190 voices, the Boston Festival Orchestra, and dozens of jesters, actors, acrobats and dancers.As directed by Derron Wood of New London's Flock Theater, conducted by Chorus of Westerly music director George Kent and choreographed by Robin Rice, these performances are radiantly dedicated the Feast of Fools and the last of the 12 festive days of Christmas.

As directed by Derron Wood of New London's Flock Theater, conducted by Chorus of Westerly music director George Kent and choreographed by Robin Rice, these performances are radiantly dedicated the Feast of Fools and the last of the 12 festive days of Christmas.Now, despite all that, let's up the ante a bit.

Now, despite all that, let's up the ante a bit. This year's presentation marks the second episode in a massive five-year story arc by scripter Harvey Blanchette. Set in a mythical world of four culturally and geographically separate kingdoms - Mirden, Zhora, Mahabala and Kasai - the ongoing story incorporates the traditional theme of Good versus Darkness and uses many familiar Twelfth Night elements. At the core is the story of a prophecy stating that a child will be born with grandparents from each of the four nations and that he will grow up to triumph over evil.

This year's presentation marks the second episode in a massive five-year story arc by scripter Harvey Blanchette. Set in a mythical world of four culturally and geographically separate kingdoms - Mirden, Zhora, Mahabala and Kasai - the ongoing story incorporates the traditional theme of Good versus Darkness and uses many familiar Twelfth Night elements. At the core is the story of a prophecy stating that a child will be born with grandparents from each of the four nations and that he will grow up to triumph over evil.While Blanchette has come up with a rich and multifaceted fantasy narrative that sustains the audience from one year to the next, he also knows that each year's individual production must work as a stand-alone story.

While Blanchette has come up with a rich and multifaceted fantasy narrative that sustains the audience from one year to the next, he also knows that each year's individual production must work as a stand-alone story.Blanchette says the writing experience is far different than if he were simply writing five connective "Lord of the Rings" or Harry Potter style novels on his own.

Blanchette says the writing experience is far different than if he were simply writing five connective "Lord of the Rings" or Harry Potter style novels on his own."I originally developed an overall, comprehensive story arc," Blanchette says, speaking by phone in the final days of intense rehearsal. "I had to do that so I didn't write myself in a hole by concentrating on just one year at a time. So I always sort of know what's happening and will happen. But a lot changes."

"I originally developed an overall, comprehensive story arc," Blanchette says, speaking by phone in the final days of intense rehearsal. "I had to do that so I didn't write myself in a hole by concentrating on just one year at a time. So I always sort of know what's happening and will happen. But a lot changes."Blanchette says the input of Kent and Wood and the performers, as each January's productions evolve during rehearsal and logistical planning, are invaluable and make him think of plot adjustments on the fly. For example, one night last week, Blanchette worked until 3 a.m. because 10 minutes had to be cut from the script.

Blanchette says the input of Kent and Wood and the performers, as each January's productions evolve during rehearsal and logistical planning, are invaluable and make him think of plot adjustments on the fly. For example, one night last week, Blanchette worked until 3 a.m. because 10 minutes had to be cut from the script."Once you start working with a director as wonderful as Derron - who understands the whole process - you learn as a writer to let certain things evolve and happen. Maybe an actor is so good in a specific role that it suggests new aspects to the character. Or a dancer might be so amazing that you change that character."

"Once you start working with a director as wonderful as Derron - who understands the whole process - you learn as a writer to let certain things evolve and happen. Maybe an actor is so good in a specific role that it suggests new aspects to the character. Or a dancer might be so amazing that you change that character."The whole interactive experience has been everything Blanchette hoped it would be.

The whole interactive experience has been everything Blanchette hoped it would be."It's always fun if you feel a narrative is part of a bigger story - as long as each one is separate and driving forward the series," he says. "And in the context of 'Twelfth Night' and its traditions, it just seemed a great challenge."

"It's always fun if you feel a narrative is part of a bigger story - as long as each one is separate and driving forward the series," he says. "And in the context of 'Twelfth Night' and its traditions, it just seemed a great challenge."

"A Celebration of Twelfth Night," Chorus of Westerly's George Kent Performance Hall, 119 High St., Westerly; 1, 4 and 8 p.m. Sat. and Sun.; $24-$68; also, preview 7:30 p.m. Fri. with tickets $18; (401) 596-8663, chorusofwesterly.org.