BY STEVEN ROSEN

As there are smart phones, cars and homes, there are a growing number of smart rock-music festivals.

By that I mean something more than those that are astutely booked to show breadth and depth of their line-ups (Bonnaroo, Coachella), or clever niche appeal (Ponderosa Stomp). Rather, these other festivals believe they can smarten you up - educate you - about the connections between new rock, especially that with an alternative bent, and other types of creative music, including classical, contemporary jazz and avant-garde/experimental. And they also just want to have fun.

Fests like New Orleans Jazz & Heritage and South by Southwest long ago taught us the connections between rock and traditional jazz, blues, R&B, folk and country - so this is the new frontier. Such "smart" fests include All Tomorrow's Parties, England's Meltdown, Cincinnati's MusicNOW, Cambridge's Beeline, and BAM Next Wave in Brooklyn.

And also Big Ears in Knoxville, Tenn., which completed its second year during the final weekend of March. Based on the quality and imagination of its approximately 55 performers, the beauty of its major venues, the attentiveness of the audiences, and the general coolness of downtown Knoxville, this is becoming the smart-festival standard-bearer. It is founded by Ashley Capps, who also organizes Bonnaroo. At the end of Big Ears 2010, he said he'd soon start work on the 2011 edition.

He'll have to go some to beat 2010. It featured as artist-in-residence the 74-year-old minimalist composer/keyboardist Terry Riley, a guru-like figure with his long white beard and kindly smile. During the weekend, he performed solo and with both jazz- and classical-oriented combos, including one featuring his son, guitarist Gyan.

With an almost-20-piece version of the Bang on the Can All-Stars, Riley did a fantastic, long-after-midnight performance of his 1964 "In C," which begins on a C and features individual musicians repeating short patterns. Over the years, Riley has studied Indian raga vocals, and his use of chanting and calm, meditative singing gave this "In C" - a landmark of Western modernism - an Eastern spiritual dimension that only enriched it.

So, too, did the concert setting - downtown's 1,600-seat Tennessee Theatre, a restored 1928 movie palace that has a curved interior and luxuriously golden Baroque decorations and looks like a Turkish palace. "It's like being inside an Easter egg," said an admiring Shara Worden (My Brightest Diamond), while performing her exhilarating Sunday evening set there before a fest-closing performance by Brooklyn's The National.

The other major site, downtown's nearby 100-year-old Bijou Theater (also restored), was smaller and less opulent but also had wonderful sound. Other venues included an interesting club on Market Square called the Square Room, which shared a glass wall with a restaurant so you could watch diners eat and read newspapers while listening to, say, a Tennessee solo guitarist using the name Mountains of Moss create sampled, looped ambient soundscapes suggestive of a forest on a calm day.

The National used its Big Ears gig as a showcase for songs from its upcoming alt-rock album, High Violet, which seem to highlight U2ish group shout-out vocals - and revved-up bursts of rousing song-ending rhythm-guitar work - as counterpoint to Matt Berninger's moody, tense, Ian Curtis-style baritone singing.

Yet despite the use of horn arrangements and extensive violin work by Padme Newsome, the set featured some of the least experimental music of the weekend. (It was rivaled in that department by Vampire Weekend, whose sold-out Saturday night Tennessee Theatre set of punkish but friendly, world-music-tinged rock had the crowd on its feet and screaming start-to-finish. At the very least, they're the new Weezer.)

Ironic, then, that one of The National's guitarists, Yale-educated Bryce Dessner (the other is his brother, Aaron), was Big Ear's co-curator, and has emerged as perhaps the rock world's biggest advocate of festivals like this. (He founded the smaller MusicNOW in his native Cincinnati five years ago. It is held immediately after Big Ears.)

Dessner, himself a New Music composer, brought plenty of other rock-tinged (or not) experimentalists with him. One was Newsome's chamber group The Clogs, which features Dessner and used Big Ears to debut The Creatures in the Garden of Lady Walton. Dessner also appeared with Bang on a Can All-Stars for "In C."

But as busy as Dessner seemed, the electrifying young New York composer/keyboardist Nico Muhly seemed even busier - nearly omnipresent. A strong candidate for my favorite Big Ears set was one at the Bijou featuring Muhly with two singer-songwriters, Sam Amidon and Doveman (Thomas Bartlett), and viola player Nadia Sirota. Among the set's highlights was Sirota playing to a Muhly-created tape loop of Antony's recorded voice, and a group take on a haunting old folk song, "The Only Tune," that Muhly's family taught him.

On the latter, the group - with Amidon on banjo - built up the song's mournful, Americana qualities but then also deconstructed them with discordant atonality, before singing "Oh, the dreadful wind and rain" like a resigned, touching refrain of all life's pains. Strong, mesmerizing, transcendent stuff. (It's on Muhly's new album, Mothertongue.)

Of the alt-rock bands that I caught, London's The xx trio made the most startling impression during a Friday night set at the Bijou. For such a young band, it had dramatically theatrical lighting - worthy of Tom Waits - and started the show with only its shadows visible behind a stage curtain. Its music was twisty, downbeat, restrainedly romantic. Simultaneously dark and gnarly, minimalist yet textured, it left a powerful impression. Its co-vocalist and -guitarist, Romy Madley Croft, was just one of several younger women who led or co-led groups in powerful experimentalist pop and rock sets.

St. Vincent's Annie Clark, also at the Bijou, compensated for her small voice with powerful use of guitar feedback, pounding and beating the instrument to get noise and jumping backward and forward with a startle, as if getting a shock. Quite literally, her band's set seemed electrifying. But for all that, it was most notable not me for a lovely melancholy cover of Jackson Browne's "These Days," which she introduced as a Nico song. (Nico recorded it on her Chelsea Girls album.) That revealed a lot about her influences.

I'm not sure if Joanna Newsom's densely textured and arranged pop music qualifies as rock or even pop - The New York Times has called her "alt-harp" - but she has the kind of adoring following that is characteristic of cult rockers. They were out in force at her headlining Bijou show. Tiny compared to her harp, with long flowing hair and a broad smile, she had a magnetic stage presence, which she needed given the time she spent tuning her harp. (She also played piano.)

At their best, the songs she and her five supporting musicians played had colorful arrangements, and songs from her Have One on Me album benefited, especially the title one. She was also in strong voice, with an especially clear soprano range. That said, there were still times when the songs and lyrics seemed to go off somewhere private, resisting accessibility as they hunt for something mythic and enlightening. Incidentally, Saturday Night Live comedian Fred Armisen opened for Newsom, doing his mildly amusing impersonation of drumming instructor Jens Hannemann.

It'd be great if next year Big Ears introduced this crowd to some of the still-active lions of Free Jazz - Ornette Coleman, Cecil Taylor or Anthony Braxton would all make great artists-in-residence. And, it'd be terrific to hear some of the more barrier-breaking vocalists/songwriters of jazz and soul - Abbey Lincoln, Andy Bey, Eugene McDaniels if he's still performing, and some younger people they have influenced.

That way, Big Ears would get even smarter.