YEARS AGO, director Aaron Posner caught flak from traditionalists for weaving Beatles songs into a production of "As You Like It." He was, and remains, unbowed. "Shakespeare would have loved the Beatles," he asserts enthusiastically.

Posner's enduring confidence in the Bard's pop sensibilities helped shape his take on "Twelfth Night," onstage at the Folger Theatre. Contemporary music is again a key part of the mix, with playwright-musician Craig Wright assuming the Lennon/McCartney role. "Craig has a kind of poetry in his language," Posner says. " 'I Bicycle Miles' [a wistful ballad sung by David Marks as Sir Toby Belch] is a song that Shakespeare would have loved, I can't help but think. There's a sort of whimsy -- a complexity of the language but with a very simple structure."

Inspiration for the marriage of Craig and Will struck when Philadelphia-based Posner received a CD of Wright's band, Kangaroo, as he was mulling a return to D.C. for "Twelfth Night." Something clicked. "I was listening to [a track called "Thing for You"] one day while I was reading the play and I went, 'You know, there's something in the spirit of this song that feels so right about the spirit I want to have underlying this production,' " he recalls. (The song now serves as a giddily raucous coda.)

Posner ran the idea past his good friend Wright, who eagerly offered his catalogue of songs with both Kangaroo and its earlier incarnation, the Tropicals. "Once I started listening to all his music, I found there were many songs that already lent themselves very, very well to the things I wanted to bring out in the play and in the characters," Posner says. "There are a number of songs in the script of 'Twelfth Night,' and most of the songs I use in the play, I use in the same place Shakespeare used them. I have added a little bit more -- things like having Sir Toby sing 'I Bicycle Miles.' There is this place where Toby changes diction entirely, and there was an energy that shifted. [Adding the song] gave us a way of accessing a more heartfelt side of him."

Still, there were a few spots for which Posner couldn't find exactly what he wanted. So Wright composed three new songs specifically for the production, including "Down to Love," a delicate tendril of folk-pop inspired by Shakespeare's textual allusion to love as rain and sung as a kind of Greek chorus throughout the play by Sarah Marshall's Feste.

"One of the things that makes 'Twelfth Night' one of Shakespeare's greatest plays is that it will bear a lot of different readings: very dark, dark tones all the way up to completely farcical, not-a-ray-of-darkness frivolous qualities," Posner says. "I felt this music would hopefully help us hit the right balance for what I was interested in, a celebration and an exploration of the courage it takes to love, that would give it a positive spin but keep some of the complexity, the slight melancholy that I find so resonant."

Pop goes the Shakespeare: James Sugg as Sir Andrew Aguecheek and Sarah Marshall as Feste in a music-filled "Twelfth Night."