Luke BryanLuke Bryan is fighting a cold on this usually stormy day in Los Angeles, but you certainly wouldn't know it by hearing him sing. The country star has done a lot of growing between his first and second albums -- not only in sales, recognition and fan base, but also in sound, as he pushes his vocals to new heights on songs like 'Do I,' 'Rain Is a Good Thing' and his countrified version of One Republic's 'Apologize,' all tracks on his critically-acclaimed sophomore album, 'Doin' My Thing.'

Luke performed two of those new songs, along with two old favorites, in our Sessions studio, nailing each performance like an old pro. And he had a little help from some famous friends ... Lady Antebellum just happened to be on the west coast for their own Sessions taping, so the trio stuck around to harmonize on Luke's first No. 1 song, which he co-wrote with Lady A's Dave Haywood and Charles Kelley, 'Do I.' We caught up with Luke after this rare treat of a collaboration.

Congratulations on your first No. 1 song, 'Do I'! Where were you when you heard the news that you were on top of the charts, and how did you celebrate?

I was at my wife's family's down in Sandersville, Ga., and I was up on the phone late at night when I got the call from my manager. I remember laying in the bed, staring at the ceiling. I didn't even really sleep at night, and I had a hunting trip planned. So the next morning, I had to get up and head straight to the airport. It kind of bummed me out, because I didn't get to celebrate with my family like I wanted to, but all my buddies that I went hunting with, we celebrated a lot! To have your first No. 1 as an artist was everything I could have ever dreamed for. Now we're keeping our fingers crossed and hopefully we'll have many more, but there's certainly nothing like the first one.

And on top of that, the fan reaction has been incredible ... Some people are saying the song is like free marriage counseling!

I've had so many people come up to me and thank me for saving their marriage, or thank me for letting them see the light and move on down the road to something else. I think that's what makes a song great -- if it really moves people or gets people thinking. 'Do I' makes couples step back, asses their situation and hopefully get in the trenches and work it out.

Tell us about your new single, 'Rain Is a Good Thing.'

Growing up in Georgia, my dad was a farmer and we worked in agriculture, so we were always looking up at the sky, checking if rain was in the forecast. That always set the tone for the mood in my household, whether we had rain coming in or not -- we knew the crops would be good and it was going to be a good week around the Bryan household. I wrote 'Rain' with one of my best friends in the world, Dallas Davidson, and Dallas and I used to have the saying, "rain makes corn, and corn makes whiskey." If we were a little bummed out about the rain -- if we had a fishing trip planned and a big rain storm was coming through, we'd be like well, rain makes corn and corn makes whiskey, and that would make us feel a little better about it.

'What Country Is' dispels some misconceptions about people who are "country." Which of those misconceptions bother you the most?

You see a lot of people out there that say they're country, and they do their little things that are stereotypical country things, but being country is a way of life. The song says it's something you're born with. Your family's a country family. They go to a little country church and do things that country people do. It ain't a rebel flag that you bought at a mall. It's more than that. It's not just about getting a John Deere hat and dirtying it up. Its actually about wearing that John Deere hat for a long time and dirtying it up because you've been working in the fields.

When you decided to cover 'Apologize' on the record, were you worried about what the guys in One Republic would think?

Yeah, I kind of had a freak out moment where I called everybody I knew and double checked with them going, "Is this the right thing to do?" And in the end, the fans were what really made me record 'Apologize.' We would do it in live shows and we'd go online and check, and so many people were commenting about it. I've often wondered what the guys in One Republic would think. I hope they hear it and enjoy it and understand it's hopefully a nice spin on a really a great song.

Do you feel you were more challenged vocally on this record than with your first?

I think I'm a different singer on this record. My first album, I was still learning who I was as an artist, learning my voice, learning my limitations on writing songs and singing. And from the time of 'I'll Stay Me' to 'Doin' My Thing,' I did 350 shows that exercised my voice a lot and learned the parameters of my voice. I always go to my producer Jeff Stevens and I'll have this new song that I'm writing and it's so high. I'm all pumped up because it's got some high notes in it, and he always pulls the reigns back a little bit. He's like, "Remember, you've got to sing this thing night in and night out." So I've enjoyed being able to expand my horizons with my voice a little bit, but in the end, my producer Jeff pulls the reigns back and makes sure I'm doing it in the keys that won't be blowing my voice night in and night out.

With 'I'll Stay Me' and 'Doin' My Thing,' your album titles seem to have a theme, that you're not going to let the business taint you. Is that more about having creative control or just about being honest with your fans?

I've always been a teamwork type of guy ... a little too much. I probably ask too many opinions, but with my label, they've always allowed me to do the music that I want to do. If I wrote a song that was great enough to be on the album and felt the conviction to put on the album, nobody's ever said a word. I've never had to walk around saying I'm just doing my thing, but in the end I do want that side of me expressed. To be successful, that's what you have to be in this business -- do your thing and the people that love your thing will flock to it, and the people that don't maybe they'll give you a shot one of these days.

What's been one songwriting session that generated a lot of laughter?

I'll never forget when me and Jason Matthews wrote the line, "Don't be a tape player hater," in 'Country Man,' I don't think I ever laughed harder. We didn't know where we were gonna put that in a song, but we knew we had to make it into a song. I just remember laughing and being so proud of such a goofy little line.

What can you tell us about the song you recently wrote with Darius Rucker?

We had a great time writing. I remember sitting in the writing session, and I would say a line and then Darius would sing it in Darius' signature voice. It's amazing how he has a vocal style that's his own. We wrote a song called 'Rock 'N Roller,' and its about back in his rock 'n roll days ... It's a fun little song that says a lot of funny little lines in it, and we still get together and recite the lines from it and get a laugh.

Think back to that moment when you told your parents you were moving to Nashville to pursue your dreams. What was their reaction?

They were honestly very excited. I've always had a real supportive family that's always been behind me in my musical endeavors. My dad, I was working for him at the time, and he essentially told me to get out of town and go chase my dreams. And my mother ... anytime a mother sends their baby boy off somewhere far away, she was really upset about it but very supportive. Every chance she can come to Nashville and see me, she does.

And now you're a dad yourself, with a toddler son and another baby on the way. What has surprised you the most about fatherhood?

Being a musician, how much work it is and [wife Caroline] being by herself so much. Out here on the road, it's a job that never stops, and to watch your child go from this little child that is so depending on you to grow to where they're pulling the blinds back in the door and watching you walk up the steps when you've been gone for a long time ... Caroline calls me and she's like, "Please talk to Bo, he's been saying your name all day." That's the best part of fatherhood. It's so rewarding to watch him grow, watch him learn, show him tractors and airplanes on the computer and then go down the street and he's freaking out when he sees a tractor. It's fun making him like the little things that you want to make him like.