Blood is thicker than water, but for the Avett Brothers, music is thicker than blood. It's not just a moniker -- Scott and Seth Avett really are related, and they've been playing together since they were kids. But 2000 was the year they started releasing their signature blend of fervent bluegrass and folk. Fifteen adventurous years later, the North Carolina indie rockers have released four EPs and eight full-lengths (with another on the way), earned a Grammy nomination, played a few late-night TV guest spots, and have been heard on shows like Parenthood and One Tree Hill.

But if one attribute stands out over the Avett Brothers' varied career, it's that they are gentlemen. Their approach to soulful, traditionalist Americana is stark yet rich, sometimes sarcastic, often existential. But their technique is especially unique in the light of their contemporaries, because it is unambiguously honest.

Stylistically, the Brothers are all over the place. "If It's the Beaches" reflects on not deserving forgiveness, and on "Murder in the City," they preach graceful nonviolence over revenge. They are metaphorically overwrought on "The Ballad of Love and Hate," yet tender and romantic on "January Wedding." In fact, they've got a lot of love songs, but this one explains it best why they succeed: "She keeps it simple / And I am thankful for her kind of lovin' / 'Cause it's simple."

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Wanting to see how the Brothers have been doing, we called Bob Crawford, who has been with the band since the early days. You know Crawford best for wielding the double bass, but his tenure with the band has, as he says, proved to be as close as family.

"It feels good that we've invested this kind of time, effort, and care into something that has grown personally for us," Crawford says. "The crowds have grown, and the size of the venues have grown, and the band has grown, as far as the amount of people on stage, but we've also been able to grow personally and creatively and keep it all under one roof. It's a great feeling of satisfaction and pride being able to do that."

Crawford says that the band is "well on our way to a new record," pointing to a late 2015 to mid-2016 release. Most of it was recorded last November live in studio, something Crawford says the band hasn't done since Emotionalism, arguably the band's breakout record.

"I feel comfortable saying [this new album] will be somewhat of a departure. But the essence of what we are and what we do will remain. The Avett Brothers people have always known-- and some people have loved -- is very well represented and reflected," Crawford says. "We had seven people recording at the same time and that was kind of a return to how we used to do it . . . So I think that the documentation of the stage band, in and of itself, is a departure and will be a progression."

As with the band's last three releases (starting with I and Love and You), they'll be working closely with mega producer and Def Jam founder Rick Rubin, known best for his work with Red Hot Chili Peppers and rap artists like Run-D.M.C. and Jay-Z. Though a hip-hop producer working on an indie country album may seem unorthodox, Crawford says, the recording approach to each genre is very much the same.

"The first thing to do is solidify that beat. What's that beat gonna do, what're the drums gonna do? Everything builds on top of that," Crawford says. "Now imagine, if you can, that you came up producing rap records, that's very essence of any rap song, is the beat, I can see that being a similar approach for Rick."

Working with Rubin, who has produced dozens and dozens of albums since the '80s, might be a little intimidating for some. And, Crawford admits, shyness was a natural reaction.

"I brought the intimidation to the table, he didn't . . . You just realize the guy on the other side of the glass, who he is and everything he's done and can provide, that can make you feel uncomfortable and intimidated," Crawford recalls. "The reality of the situation is that I've never seen [Rick] treat anyone other than very kind and sweet. He's very flexible and relaxed and poised and very understanding about mistakes and this and that. He wants to create a positive work environment for everyone. I was pretty uncomfortable the first couple days I ever worked with him, but I'm pretty sure that was my fault, not his."

Besides Rubin, another staple of the Avett Brothers is their series of songs about attractive women. There's at least 11 of these songs, including "Pretty Girl From Locust," "Pretty Girl From San Diego," "Pretty Girl From Chile," and even "Pretty Girl at the Airport." Stylistically, each song varies as widely as the diverse regions in question. But are these women real?

"I guess in some way, they're somewhat real," Crawford says. "You can show appreciation and affection in many ways. They're not all songs about girls that were girlfriends or this or that, but a lot of them are like a tip of the hat. There's an instrumental that we played live. I don't think we played it recently, but I believe that has a Pretty Girl title. We recorded it, but it never made a record. I think it's called 'Pretty Girl From Here.'"

In mid-2011, Crawford took a short hiatus or two from the band after learning his daughter, Hallie, had a brain tumor. She went through treatment in 2011 and 2012 at St. Jude's Children's Research Hospital in Tennessee and recovered, but the cancer returned in 2013, so little Hallie, now 5, went through treatment again. Last year was the first time the Crawford family did not have to deal with cancer.

"It's a kind of cancer that's very aggressive. It doesn't go away very easily. You could not have it for five years and it could come back," Crawford says. "She's still in the zone where it's a high risk of occurrence, so we gotta get keep going that's all. We gotta keep going."

I wouldn't say it's in remission. In fact, we go next week to get her checked out, she'll get an MRI scan and we'll see where we stand. We go every three months. And this will be 20 months," Crawford says. "But 2014 was a year of just watching it, just watching, there was no new cancer to report, no new tumors, no you know."

"We felt very blessed to have that year and we hope 2015, hopefully we can kick it off right . . . We got a ways to go yet," Crawford says. "She seems to be doing great. You can't look inside her head, but to be around her, she's doing just phenomenally. We hope that what's on the outside is on the inside and we just keep praying for that."

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