The fearless

Esperanza Spalding

likes a good challenge. And she's up for one here tomorrow afternoon.

When this exceptional, "triple threat" jazz bassist, singer and composer hits the Festival Pier stage as part of The Roots Picnic, most people will still be looking for parking.

"From what I'm hearing, I may be the first performer on," she clued in a recent chat. Adding insult to injury, readers of this column may be the only ones to know that the 23-year-old Spalding is on the bill.

While informed by the same sort of progressive, genre-mixing spirit that drives festivalmates such as The Roots, Gnarls Barkley, Sharon Jones and the Dap Kings and Santagold, Spalding was a late add and has not been touted in show advertising.

And unless you caught her national television debut on "Late Night With David Letterman" two nights ago, you've probably not heard her music, including the just released "Esperanza" album.

But like the TV show's host and its musical director, you're likely to get a very positive first impression. "You're right, Paul [Shaffer], the coolest artist we've ever had on the show!" exclaimed Letterman after Esperanza and her band swung and swayed through the telling, jazz pop ballad "Precious."

That tune kinda pegs her in a Corinne Bailey Rae (neo-soul pop with jazz inflections) vein. In truth, this New Millennialist digs way deeper into the mines, hauling up a major lode of creative bass and vocal styles, from bebop to funk fusion to free-form jamming accented with wordless vocalese.

In fact, her two voices (sung and instrumental) are so intertwined, it's difficult for her to deliver just one without the other. "I recently cut a track singing with Fourplay, and it was so hard without the bass in my hands," she said.

Offspring of a Spanish-speaking, jazz-loving mom of Welsh, Hispanic and Native American descent, and an absentee father who's black, Spalding grew up in Portland, Oregon, hearing all kinds of music, from oldies rock to female R&B/hip-hop role models TLC and Salt-n-Pepa.

Her cultural roots (and the influence of a Cuban-born babysitter) are most evident in Spalding's vibrant rhythmic orientation - heavy on Latin, African and especially Brazilian flavors.

On the "Esperanza" album, the tri-lingual singer won me over from the git-go with a haunting performance in Portuguese of a Milton Nascimento song, and with her fluent, Spanish language version of the jazz classic "Body and Soul," done in rare and sprightly 5/4 time. And her smart originals hold up well in that heady company.

Spalding's overriding goal as a jazz-rooted musician is to "make it palatable and grooving - something that someone who isn't schooled in jazz might ingest and appreciate," she said.

So the challenge of playing tomorrow before people who've never heard her is just part of the process of discovery for herself as well as them, Spalding shared with enthusiasm.

"You get to see how people really react to you. They come to you unaware, holding out a clean plate. So if they respond positively, not knowing in advance what you're doing, that's the best kind of feedback you can get."

Spalding has been pushing herself musically since early childhood in Portland. "Maybe a little A-D-D," she had trouble with subjects that didn't interest her and spent years being home schooled. But she was always a quick learn and serious student of music, starting at 5 with classical violin.

A decade later, she casually picked up a concert bass in a school rehearsal room. A music teacher taught her a single blues line, and she was off to the races. A couple of months later, the then 15-year-old was gigging professionally with a band of seasoned players and, within a year, was working with "maybe six or seven different groups" as a player and singer, including the jazz-rock group Noise for Pretend, which recorded two albums.

Then and now, Spalding argues that a player should always try to work with musicians much better than yourself, " 'cause they'll kick your butt!"

After earning her GED, she matriculated at Portland State to pursue music studies. Not for long. A professor suggested she was good enough to get into Berklee, the prestigious, jazz-oriented Boston music school that's turned out a gazillion first-rate pros.

The next year, Spalding was at Berklee on a full scholarship. She quickly established herself as one of the school's best players, winning ringing endorsements from senior faculty member Gary Burton and returning alum Pat Metheny, who declared she had something extra special - an "X Factor" - about her.

"At the time, I didn't know how he meant it," Spalding said. "But it was a real boost. I was financially strapped and depressed, literally dragging my bass two miles through the snow to get from the place I was staying to the train station to get to school. It was at a point when I was trying to decide if I really wanted to pursue music as a career, or do others things, something more socially responsible."

Also in the nick of time, singer Patti Austin gave Spalding her first big professional break, hiring the then 19-year-old after one audition to play bass on Austin's "For Ella" (Fitzgerald) tour, which traveled on-and-off for a year and a half through the U.S. and Italy.

Berklee's the kind of place where profs look the other way and smile when their students skip out for gigs, so no problem there. And Austin really became Spalding's road scholar.

"Patti's a hard-core doll, super warm, super generous and that all comes off in her musicianship," Spalding shared. "Unlike some people I've worked with, she took the time to teach each of us about playing with her. These were lessons you can take anywhere, that opened the door for all kinds of other gigs."

Among them, touring with Berklee sax teacher Joe Lovano and creating Esperanza's first, "more experimentally" minded album project called "Junjo" (with pianist Aruan Ortiz and drummer Francisco Mela). Recorded as her senior thesis, the project turned out so well it won commercial release on the Ayva label three years ago.

When Spalding graduated ahead of schedule in 2005, Berklee continued to support her, inviting the 20-year-old to join the faculty. (Only Metheny was younger, 19, when given the same honor.)

"And the deal they offered for me to teach was with the understanding that it shouldn't get in the way of my professional career," Spalding said. "I'm taking this next semester off, to tour and work the record, but I'm really missing teaching and want to get back to it in January."

Given how well things are now going for Esperanza Spalding, winning new fans literally every day, I'm thinking she may have to extend that leave of absence. Lend her your ears, Picnic goers, and see if you don't agree. *

Penn's Landing Festival Pier, Columbus Boulevard and Spring Garden Street,

2 p.m. tomorrow, $49.50, 215-336-2000, www.livenation.com.