Spoleto Festival USA is built on several crucial cornerstones, without which the entire enterprise would falter or collapse.

The materials for three of those cornerstones are derived from classical music, annually fired in the festival kiln.

The Spoleto Festival USA Orchestra, Westminster Choir and Chamber Music Series conspirators each make essential contributions that have defined the international arts event since its inception and continue to generate the bulk of the energy required to keep things going.

The operas - three this year - depend on the orchestra (or parts of it), of course, as well as the singers of the choir who typically do double duty as opera chorus members. The festival offers two big symphonic concerts that showcase the talented young players carefully selected through a rigorous audition process. And the Westminster Choir also presents two ambitious programs each year.

The chamber music series, organized by Geoff Nuttall, is among the most exciting and diverse offerings of the festival. A sizable core of top-drawer musicians, supplemented by special guests, perform two concerts every day - 11 separate innovative programs over 17 days - that never fail to thrill patrons, some of whom are certifiably obsessed with the undertaking and show up repeatedly at the Dock Street Theatre.

The festival provides additional opportunity to admire the skill and flexibility of its musicians and experience repertoire that's not so mainstream or regularly programmed by other organizations.

The Intermezzi series, organized by Resident Conductor and Director of Orchestral Activities John Kennedy, tends to give certain festival participants a chance to break free of their regular responsibilities and present something a little different or enjoy the warmth of the spotlight.

And the Music in Time series this year includes programs dedicated to the works of Alaska resident John Luther Adams, who just won a Pulitzer, Danish composer Hans Abrahamsen, French composer Tristan Murail and Dutch composer Louis Andriessen. The series provides one of the best opportunities in Charleston to hear recent classical music played extraordinarily well, and don't assume it's all esoteric, inaccessible stuff.

These days, composers are less interested in bucking tradition or flaunting their avant-garde credentials and more concerned with producing evocative soundscapes and reworking known forms. Adams' work, for example, is inseparable from nature (or at least the idea of nature); and Andriessen's version of minimalism is brash and fun.

Indeed, a trend seems to be taking shape among the festival's musical offerings, a general inching forward in time. Increasingly, 20th- and 21st-century works are finding their way onto programs large and small. This is partly due to the influence of Kennedy, an accomplished percussionist and composer who has long been in charge of the Music in Time series, which is explicitly dedicated to new music.

But there are other forces at work.

"There's been a gradual evolution in what is relevant, in what are the pieces of repertoire we can give context to in the festival itself," Kennedy said during a break in a rehearsal of the Michael Nyman opera "Facing Goya."

Nyman's instrumental chamber music will be the subject of a special concert at the Sottile Theatre on May 26, with the composer in attendance. The English composer, who specializes in a kind of minimalism informed by popular tropes, is perhaps most famous for his film scores for "Gattaca" and Jane Campion's "The Piano," the latter of which resulted in a multiplatinum album.

Kennedy said the work of another living composer, John Adams (not related to John Luther Adams), also will feature prominently this year. His opera "El Nino" is on offer, along with his Dr. Atomic Symphony. Last year, the festival orchestra performed Adams' "Harmonielehre," an invigorating work that was very well received. This is the "context" to which he refers.

What's more, audiences have come to expect innovation, "they are willing to have new experiences," Kennedy said. The spirit of adventure is widely embraced. "Many of the best-loved or most talked-about productions are those that have pushed (audiences)," he said.

Besides "Facing Goya," Kennedy is scheduled to conduct the orchestra in a concert about Beethoven that will feature the Seventh Symphony along with two modern works that reference it by Louis Andriessen and by Michael Gordon of Bang on a Can fame.

Andriessen's "The Nine Symphonies of Beethoven" is a 10-minute-long mashup, one of the composers earliest pieces that will be offered for the first time in the U.S.

Gordon's "Rewriting Beethoven's 7th Symphony" is "aggressive and loud," Kennedy said. "It's the brutal Beethoven." And it deconstructs the original work in fascinating ways.

The 20th century was good to choral singers, and the Westminster Choir is taking advantage of the fact. In one program it's presenting works by Daniel Elder, Latvian composer Eriks Esenvalds and Maurice Durufle. In another, an early setting of the Te Deum hymn of praise by Handel will be balanced by a 1985 version by Arvo Part. The Charleston Symphony Orchestra will join the choir for these Te Deum performances.

So then perhaps it's not our imagination. Recent classical music dominates. There is no Tchaikovsky symphony on the program, no opera from the standard repertoire, no Verdi or Brahms Requiem, no Rachmaninoff piano concerto. Spoleto Festival USA is embracing its purpose and inviting patrons to open their ears.

And it's doing so always while striving for the highest standards.

"One of the things we have at the festival is an ethos that really inspires everyone to give their best, just because it's so ephemeral," Kennedy said. "It goes up and comes down so quickly."

So catch it while you can.