BOSTON (Reuters) — British disc jockey Paul Oakenfold, known for high-energy sets in sweaty nightclubs, will follow a different beat this summer in his first-ever performance with a full orchestra in Boston’s 107-year-old Symphony Hall.When Oakenfold mixes his electronic music with the Boston Pops in a June festival where the Cowboy Junkies will also fuse their haunting, country-tinged rock with one of America’s oldest city orchestras, both acts will join one of the fastest-growing musical genres — “classical crossover”.

Though a death knell for classical music rang a decade ago when British critic Norman Lebrecht wrote the book “Who Killed Classical Music?”, U.S. orchestras have largely defied doomsayers as operating revenue and digital music sales grow. But as its audience greys, public music education disappears from schools and classical programming fades from mainstream television and radio, many ensembles are scrambling to reinvent themselves to court a younger demographic.

Indie pop band the Decemberists will perform in July with the Los Angeles Philharmonic and with orchestras in Atlanta, Philadelphia and Chicago; the Cincinnati Pops is teaming up with funk icon Bootsy Collins, and 2003 American Idol runner-up Clay Aiken is planning a summer symphony tour.

“Most symphony orchestras are not bringing in the younger audience, and the audience who is there are getting older and greyer,” said Julius Williams, a professor at Berklee School of Music and former assistant conductor at the American and Brooklyn Philharmonic orchestras.

Thanks to “crossover” acts such as poppy classical artist Josh Groban, classical was the fastest-growing musical genre in 2006, with album sales up 22.5 percent, while many popular genres fell, including rap which dropped 20.7 percent, and R&B, which was down 18.4 percent, according to Nielsen SoundScan.

A hefty 43 percent of classical’s sales came from crossover titles, while 35 percent were traditional classical albums.

The Boston Pops, famous for light classical music and family pop tunes from decades past, is in the third year of a “Pops on the Edge” series that has featured singer-songwriter Aimee Mann and soulful Kentucky rockers My Morning Jacket.

The Boston Pops, whose attendance has slipped from a high of 93 percent of Symphony Hall’s capacity in 2000 to 88 percent in 2005, performed with Aerosmith lead singer Steven Tyler and guitarist Joe Perry in an Independence Day show last year.

But conductor Keith Lockhart, in his 13th season, says he is seeking artists who fit more naturally with orchestral arrangements. “Something amplified and that loud,” he said of Aerosmith, “ends up being us just playing loud long notes as loudly as we can play, and it ends up being their show.”

“What we’ve been trying to do in artist selection from early on has been to find people who are really interested in more of a collaboration from the ground up.”

Nico Muhly, a 26-year-old New Yorker who has worked with innovative Icelandic singer and composer Bjork, has written an Indonesian gamelan-influenced arrangement for the Boston Pops’ EdgeFest concerts in June that also feature Oakenfold.

Oakenfold typifies nearly everything the Pops are not <\m> an electronic-based musician who pioneered the “trance” genre of dance music, using two turntables in pumping sets that have opened for Madonna and U2 <\m> at fees as high as $50,000 a gig. Oakenfold will perform a live remix of music by Los Angeles composer Felix Brenner with the Boston Pops accompanying the DJ by playing sections of the arrangement, said Margo Saulnier, the 33-year-old Pops artistic coordinator.

But some critics question whether such collaborations can ever please two distinct crowds — purists who bristle at the sound of classically trained musicians mixing it up with guitarists and other artists, and a younger crowd who are quick to cringe at any softening of edgy music by an orchestra.

“To me it didn’t quite add up,” Boston Globe music critic Jeremy Eichler wrote of a May 9 Boston Pops performance with singer-songwriter Ben Folds. “With a few prominent exceptions, much of the orchestra and certainly the entire string section seemed completely superfluous.”

Lockhart said such criticism is to be expected of a new genre. “It’s one of the problems of inhabiting that weird space that we call crossover. There’s no one really specifically qualified to criticise it,” he said.

He identified Eric Clapton and the band Santana as artists he would like the orchestra to accompany.

Not all of America’s estimated 1,800 orchestras embrace the idea. The Philadelphia Orchestra is taking a different tact with its “Access” series where a host explains arrangements to the audience who can also watch the performance on screens.