GEOFF BENNETT: Two-time Grammy nominee Sierra Hull has reached the pinnacle of bluegrass on her chosen instrument, the mandolin.

Special correspondent Tom Casciato has the story of how she got there for our arts and culture series, Canvas.

TOM CASCIATO: On this night at The Hamilton in Washington, D.C., it's easy enough to hear why 33-year-old Sierra Hull has been six times named the International Bluegrass Association's mandolinist of the year.

Not as immediately clear is why "Rolling Stone" has termed her a rebel of the genre.

SIERRA HULL, Musician: Usually, I'm just kind of searching for sounds and going by feel and trying to write something that is satisfying.

TOM CASCIATO: And, indeed, she and her band are right at home with traditional bluegrass sounds.

But take the lead single from her latest album, "A Tip Toe High Wire."

It's a song called "Boom."

An American songwriter used a pretty non-bluegrassy term for it.

(SINGING) TOM CASCIATO: They called it funky.

SIERRA HULL: Funky?

All right.

I will take it.

TOM CASCIATO: I'm thinking, I wonder if Sierra Hull growing enough thought, someday, people are going to hear me and play the mandolin and say, well, that's funky.

SIERRA HULL: No, I probably wouldn't have thought about it, honestly.

TOM CASCIATO: But the song is kind of funky.

SIERRA HULL: It's kind of funky.

That's the beauty of where I have gotten to more than I would have imagined, just things, the opportunities that have come, unexpected things, because I was so lucky to have some things happen.

TOM CASCIATO: What's happened to sierra whole is extraordinary, though it started out pretty ordinary.

SIERRA HULL: We had one of those old bowlback mandolins.

TOM CASCIATO: Yes.

SIERRA HULL: We call them a tater bug where I'm from.

TOM CASCIATO: Where she's from is Byrdstown, Tennessee, population under 1,000.

SIERRA HULL: And I remember learning my first tune.

I just connected so deeply to that right away.

TOM CASCIATO: Were you good right away?

SIERRA HULL: I think it was a combination of having some natural ability, but also being fully obsessed to, where every day my dad would come home from work, he was teaching me what he knew at first, and then I was going to these bluegrass jams.

TOM CASCIATO: The jams took place at a community center, where local players would perform for crowds of 20 or 30.

SIERRA HULL: And I remember being super tiny and those local bands saying, do you want to get up here and play along with us?

I learned so much.

They weren't trying to go out and do it professionally.

They just loved it.

TOM CASCIATO: Who were you listening to at that time?

SIERRA HULL: Doyle Lawson and Quicksilver, some of those really harmony-based bluegrass Gospel albums.

Then my dad brought home a Tony Rice album called "Church Street Blues," and I remember just falling madly in love with that record.

It was a cassette tape, actually.

We used to drive around in his old Ford truck, and I remember the truck kind of ate the tape, and we were so devastated.

TOM CASCIATO: But there was one artist in particular who made the biggest impression.

SIERRA HULL: I got my first Alison Krauss album when I was 9 years old.

And that just kind of lit my world on fire.

And it made me go, this is what I want to do.

TOM CASCIATO: With Krauss as her inspiration, she buckled down and practiced and practiced.

SIERRA HULL: And I was lucky to have parents who breathed a lot of love and support into it.

If I'd ever get lazy practicing, I remember my dad saying: "You have been a little lazy lately, hadn't really been practicing too much."

He said: "Well, you know what's going to happen.

One of these days, Alison Krauss is going to call you to come play, but you're not going to be ready."

TOM CASCIATO: You wrote Alison Krauss a fan letter.

SIERRA HULL: Well, I did.

It was -- she never got it, but it was a school assignment.

Write a letter to your.

hero.

TOM CASCIATO: By sheer coincidence, I have a copy of that letter here.

SIERRA HULL: Oh.

TOM CASCIATO: Would you mind reading it?

SIERRA HULL: Sure.

Let's do it.

(LAUGHTER) TOM CASCIATO: We will get to the letter.

First, Alison Krauss was probably the most accomplished woman in bluegrass, already 10 Grammys into a career that has seen her win 27.

Sierra Hull was 10.

SIERRA HULL: "Dear Ms. Krauss, Dear Ms. Alison Krauss, my name is Sierra Hull.

I'm a very, very big fan of yours.

I'm coming to one of your festivals for the first time, MerleFest, North Carolina.

I'm bringing my half-size fiddle for you to sign so maybe one day I can show my kids how to play.

You're my hero."

And the idea of going to another state to go to a festival, let alone one Alison Krauss was at just seemed impossibly cool.

TOM CASCIATO: It got cooler when she was outside the festival playing a song by mandolin virtuoso Chris Thile, who happened to buy and must have liked what he heard.

SIERRA HULL: I look up, and Chris Thile is right in front of me.

And he says: "Holy cow.

Want to play it together?"

And I was like: "What?"

And so we went and found a little corner somewhere and he jammed with me for like an hour-and-a-half, and he took me backstage to meet my hero.

And she signed my fiddle.

TOM CASCIATO: Dream come true, right, and the beginning of a musical friendship.

Just two years later, Alison would invite sierra to perform with her on country's greatest stage, Nashville's Grand Ole Opry.

I have seen a picture of you where you're about 12 and you have got your mandolin and you're with Alison and the band and you're looking at the camera like the cat who caught the canary, like you... SIERRA HULL: To say the least.

TOM CASCIATO: What would follow was a formal music education fueled by a full scholarship to Boston's Berkeley College of Music, leading to a series of compositions and collaborations that have seen her search out directions far beyond bluegrass, among them, ethereal tracks produced by banjo legend Belarus Fleck, jazz funk jamming with guitarist-producer Cory Wong, and sophisticated rhythmic explorations with her own band.

"Rolling Stone" calls her a musical force not only in bluegrass, but in various genre circles.

But no matter how intricate the music, her approach remains straightforward.

SIERRA HULL: A lot of times, I'm just kind of going, what does the lyric demand?

What feels good on the instrument?

I will write some sort of crooked, crazy thing, share it with my bandmates.

And they're the ones that will be like, oh, yes there's that weird bar of three here.

And I'm like, OK, great.

TOM CASCIATO: Does your music have boundaries, do you think?

SIERRA HULL: I don't think so.

Those things that I love about all these collaborations I have done, combined with my bluegrass roots, I think it's kind of an inevitable thing.

You're going to get a little funky in there.

TOM CASCIATO: For the "PBS News Hour" I'm Tom Casciato in Washington.