Youth theater people say that kids are great at learning Shakespeare soliloquies because nobody's told them they're supposed to be difficult.
Evidently the same applies to music, which helps explain how much ground San Diego avant-folk-bluegrass trio Nickel Creek has covered in its nascent career.
Singer-mandolinist Chris Thile, singer-fiddler Sara Watkins and her brother, singer-guitarist Sean Watkins, have been playing together for a dozen years, yet they are still in their early 20s and only last year released their debut album, the Grammy-nominated "Nickel Creek."
Because they started so young and lucked into mentorships with some forward-thinking musicians, they don't think twice about making musical bedfellows of Bob Dylan and Bach in the midst of a bluegrass tune.
It's a lesson they learned from such modern-day players as Bela Fleck, Mark O'Connor and Edgar Meyer, who cross back and forth between folk, bluegrass, jazz and classical idioms as if they were not separated by walls, but connected via revolving doors.
That spirit quickly attracted the attention of onetime bluegrass wunderkind Alison Krauss, who signed on to produce their debut album. It's sold 159,000 copies as of Friday, according to SoundScan, which by normal bluegrass standards pretty much makes Nickel Creek the Destiny's Child of the genre.
"We grew up listening to the generation of musicians that had learned from some of the old guys--Bill Monroe and Earl Scruggs," says Sara Watkins, who shares a home with her brother in San Diego.
"Musically they were not as set by these rules about bluegrass playing," she adds. "We grew up incorporating a ton of different styles--not consciously, but just because we listened to everything."
That began with their parents, who exposed them to a wide range of music, recorded and live, starting when they were toddlers growing up in Vista in northern San Diego County.
Sean Watkins, now 24 and five years older than Sara, was taking piano lessons from a teacher whose son played in a folk and bluegrass group. Chris Thile, who has since moved to Nashville, was part of the same circle and hooked up with the Watkins siblings when he and Sara were still in elementary school.
"My teacher suggested we check out her son's band at a local pizza parlor, and it was a great band, so our family wound up going there every Saturday night," recalls Sean, whose first solo album was released in March. "We really got sucked in by the culture of bluegrass and by all the improvising."
Adds Sara: "Especially for kids, you don't get to see much real playing these days. There's the symphony, which is a great experience, but with so many kids their relationship with music comes straight out of the stereo. And it's not really music you can break down and hear the individual instruments."
Critics and acoustic-music aficionados alike have taken notice of the individual talents and collective interplay of Nickel Creek's players, whose youth and good looks have caused the group to take some ribbing as a sort of Dawson's Nickel Creek.
While the three are capable of jaw-dropping displays of technique, they also exhibit a growing maturity that subordinates instrumental prowess to the service of the song at hand.
"Fortunately," Sean says, "our teachers were great at instilling into us the value of note selection rather than licks, and that it's better to play a few really good notes rather than a bunch of notes that don't matter."
Thile, who's 21 and has released two solo albums, has described what Nickel Creek does as "boundaryless music," raising the question of how they decide what fits and what doesn't.
To answer, Sean Watkins borrows from a famous Supreme Court ruling: They can't define it, but they know it when they hear it.
"We definitely do have boundaries," he says. "The point is that if there's some element of a genre of music that fits well with another kind, we won't not blend them just because they aren't usually heard together.
"In the last two years of playing together, we're really getting to know what we want to do," Sara says. "It's important to make things sound good. If one of us hears something in our head that would help a song in any way, we're not turned off if that something is a Celtic or a classical form. If it helps the overall effect of a song, we want to try it and see if it really does."
* Nickel Creek plays Thursday at the Coach House, 33157 Camino Capistrano, San Juan Capistrano. With California Trio, Jannel Rap. 8 p.m. $15. (949) 496-8930. Also June 29 with Vince Gill at the Greek Theatre, 2700 Vermont Canyon Road, L.A. 7:30 p.m. $25 to $75. (323) 665-1927.