Constant crossovers

On a hot day at the end of June, the fashionable Brooklyn band The Dirty Projectors played a gig at London's Barbican Hall flanked by a 20-piece ensemble called Alarm Will Sound that included oboe, flute, a string section and several percussionists.

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On a hot day at the end of June, the fashionable Brooklyn band The Dirty Projectors played a gig at London's Barbican Hall flanked by a 20-piece ensemble called Alarm Will Sound that included oboe, flute, a string section and several percussionists. The concert, which was stuffed with arty-looking young professionals, was made up of two halves: in the second, the six-piece played a selection from their acclaimed 2009 album Bitte Orca, which combines R'n'B beats, complicated guitar lines and fragmented, overlapping vocals.

In the first section, they played their 2003 album Getty Address - a concept record written about a young man falling in love on the site of the historic battle at Gettysfield - in its entirety. With long instrumental sections, loose song structures, and a conductor keeping all 26 musicians on the same page, it had a lot more in common with the sort of classical concerts that are usually associated with the Barbican than a rock gig.

The strange thing about the event isn't that a pop band made up of 20-something hipsters played an hour of orchestral music with a classical ensemble. The strange thing is that this sort of concert (and this sort of musical crossover) isn't unusual anymore. There have been popular genres in the past - prog, Krautrock, ambient electro - which have taken inspiration from classical music. But it's only recently that this inventiveness has reached the fertile scene where pop, post-rock and Americana meet.

Late last year another zeitgeisty band from Brooklyn, Grizzly Bear, played at the same venue with the London Symphony Orchestra. Grizzly Bear are another band stitching orchestral influences into an indie-rock fabric. With their skinny jeans and checked shirts; traditional indie set-up of bass, drums, guitar, keyboard, vocals; and fashionable postcode, they could be any other rock band, before they open their mouths. But the quartet's close falsetto harmonies make them sound more like choir boys than rockers, and they are eager to collaborate with classical musicians (they played with the LA Philharmonic back in 2008, too).

The old complaint about rock music, usually aimed at popular, unchallenging bands, is that it has changed very little since The Beatles and The Rolling Stones. In the early Noughties, bands like The Strokes made the 1960s garage rock sound of bands such as The Stooges cool again, and it seemed that rock was indie was stuck in a retro rut. But since then, there has been a resurgence - especially in North America - of music that's big, baroque and unique-sounding, splicing up influences that span centuries.

The Californian harpist and singer Joanna Newsom's third full-length album, which was released earlier this spring, was made up of three CDs, with many tracks clocking in at nine or 10 minutes each. Although it's not as relentlessly orchestral and anachronistic-sounding as 2006's Ys, she still adds horns, strings and percussion to her mix of blues, avant-folk and jazz, as well as more obscure instruments such as the Indian tambura and eastern European kaval.

Unlike Ys, which she played live with a full symphony orchestra, Newsom has been touring Have One On Me with a stripped-down outfit that includes trombone, banjo, violin and drums. The fact that she continues to sell out concerts in minutes shows that there's definitely an appetite for her baroque, genre-defying sound. Another fusion-friendly musician whose shows sell out quickly is Owen Pallett, the 30-year-old violinist and composer from Toronto who has collaborated with the gypsy-folk wunderkind Beirut, baroque pop torchbearers the Arcade Fire and the aforementioned Grizzly Bear, as well as releasing two solo albums under the moniker Final Fantasy, and one (Heartland, released earlier this year) under his own name. Pallett studied classical piano as a child before teaching himself violin while studying composition at the University of Toronto, and although his nexus of friends and collaborators is firmly in the indie-rock world, he's still heavily influenced by much older styles.

While his first album combines new folk and chamber pop, his second is played entirely by a string quartet and the third, a concept album about a fictional world called Spectrum, features the Czech Symphony. In a Guardian interview earlier this year, he puts his carving out his own space in between the worlds of pop, punk and classical music down to the fact that the contemporary classical scene in Toronto at the time was "like wet lettuce ? totally the opposite of vibrant".

Pallett, Newsom, the Dirty Projectors and Grizzly Bear are all from North America, but a similar situation in London is propelling classical musicians into the world of pop, with exciting results. There have been a couple of attempts to bring orchestral music out of the concert halls and into pubs and bars - the regular music night Nonclassical, held in a Shoreditch nightclub, being one - but for the most part, classical music inhabits its own world. The upside of this is that classically trained musicians such as the East London 23-year-old Micachu, who released her debut album Jewellery last year, end up crossing over into other genres in weird new ways.

Micachu - real name Mica Levi - trained at the prestigious Guildhall School of Music, plays violin and viola, and was commissioned to write an orchestral piece for the London Philharmonic in 2008. But when she's not jamming with her string quartet, she's collaborating with the rockers The Golden Silvers or garage and grime MCs like Kwes and Toddla T. Her first album combined pop, garage and samples, and as well as violin and guitar, featured Levi on self-made instruments, such as a modified guitar and a bowed instrument made out of a CD rack.

Micachu has played with members of another young London band who count composers such as Philip Glass among their heroes: The xx topped lots of end-of-year best album polls for their self-titled debut, which combines gloomy electro with minimalist compositions. It would be fun to see them both on a bill with Gaggle, the 22-piece all-female choir, also from London, who are combining a cappella choral vocals with a anarchic spirit more often seen in punk or riot grrrl bands. The choir sing about life, lies and disillusionment while dressed in colourful hooded robes, and will be playing at almost all the major UK festivals this summer. Along with the TV series Glee, they're helping to make choirs cool again.

Gaggle, like Micachu, the Dirty Projectors, and dozens more bands emerging at the moment, are reaping the rewards of combining old-fashioned discipline and instrumentation with a modern attitude that says it's all right to mix up clashing sounds and write lyrics about relationships, computer games or historical battlesites. We've seen classical composition get mashed up with indie, grime, folk and electro; it's exciting to think what other strange possibilities might emerge next.