What does a rock star do for an encore?

For bass-and-keyboard player Mike Mills, a founding member of the chart-topping, globe-hopping, Grammy-winning original alt-rock band R.E.M., act two involves taking music in a whole new direction.

“I think it’s a hybrid of classical and rock and roll,” explained Mills, when asked about his latest project, “Concerto for Violin, Rock Band and String Orchestra.”

“It has elements of each.”

Elements which, in this case, spring from the divergent musical interests of two childhood friends—Mills and Grammy-nominated violinist Robert McDuffie—who met in the church choir in Macon, Ga., and went on to careers as professional musicians in parallel genres. McDuffie commissioned Mills to compose “Concerto,” with the haunting R.E.M. hit “Nightswimming”—its sweet, circular strings arranged originally by Led Zeppelin bassist John Paul Jones—as its centerpiece. The whimsical young composer David Mallamud provided additional music, and the D.C. area premier at The Music Center at Strathmore will feature McDuffie on violin with Chicago’s innovative chamber orchestra, Fifth House Ensemble, and Mills taking his usual position behind keyboard and bass with the rock band.

“The form is classical because it’s in the form of a concerto,” he explained. “Which is a piece of music that’s there to highlight the virtuosity of the soloist—in that sense, it’s a classical piece.

“There is a string orchestra—but really there’s a whole rock band in there, too. And I wrote it as six pieces of music. The defining element of strings and violin puts it into a classical world—but it’s not strictly a classical piece.”

It’s not quite rock and roll, either—but that makes sense when one considers that before Mills met his R.E.M. bandmates at the University of Georgia in Athens, he was the son of a tenor who sang on “The Ed Sullivan Show” and in the Naval Aviation Choir.

“For me, it feels very natural because I grew up with classical music all my life,” he said. “My father was a dramatic tenor so it was all around my house.

“My parents moved to Macon and chose the church where (McDuffie’s) mother was choir director because they had the best music program,” he chuckled. “As a result, Bobby and I spent most Sundays together, in handbell choir and youth choir.”

McDuffie went on to Juilliard, appeared as a soloist with the New York and Los Angeles Philharmonics; the Chicago, San Francisco and National Symphonies; and the Philadelphia, Cleveland and Minnesota Orchestras. His fondness for performing “Nightswimming” over the years led him to propose that Mills compose a longer work, specifically for chamber orchestra and rock band.

“I thought that was a fascinating idea,” said Mills. And even though he’s the guy who penned “Don’t Go Back to Rockville,” the 1984 hit (credited, of course, to Berry/Buck/Mills/Stipe in egalitarian R.E.M. fashion) that bands love to cover when they play Montgomery County, he is quick to point out that “Concerto” is musically sui generis.

“I don’t want to lead R.E.M. fans on,” he was careful to explain. “Other than ‘Nightswimming,’ there’s no connection to R.E.M.; it’s simply me and some amazing musicians. It’s a new chapter.”

Not that the music bears no resemblance; Mills acknowledged that there have always been some strings involved, off and on, in R.E.M.’s music. But it’s his second act, after all; he wants to present something new, and is hoping to capture an appreciative audience.

“R.E.M. fans have always been open-minded enough to enjoy whatever elements we chose to incorporate into the music,” he pointed out. “And I think that would carry through here.

“What I’m trying to do is find fans of music, whether they’re classical fans or rock and roll fans,” he added. “I think the idea here is that it’s just an entertaining half hour, regardless of where your origin of taste is.”

Concerto for Violin, Rock Band, and String Orchestra will begin at 8 p.m. Thursday, Nov. 3 at The Music Center at Strathmore, 5301 Tuckerman Lane, North Bethesda. For tickets, ranging from $35 to $65, visit www.strathmore.org or call 301-581-5100. View this event on CultureSpotMC here.