After 40 years together, one of America's most enduring bands enjoyed the challenge of learning new material for CMT Crossroads: The Doobie Brothers and Luke Bryan. And for Bryan, the biggest thrill was just sharing a stage with a group that he thinks of as rock royalty.

"I know they've been getting off stage and just sitting there and picking and listening to my music, and that's just been the most flattering part about all of this," said Bryan. "You give us another week and a few more rehearsals, we could take this show on the road."

CMT Crossroads: The Doobie Brothers and Luke Bryan premieres Friday (June 24) at 10 p.m. ET/PT on CMT and features collaborations on hits like the Doobies' "Black Water," "Long Train Runnin'" and "China Grove" as well as Bryan's "Do I," "Rain Is a Good Thing" and "Country Girl (Shake It for Me)."

In this interview with CMT Insider producer Terry Bumgarner, Bryan and the Doobie Brothers' Tom Johnston and Pat Simmons talk about finding common ground for rock and country, refusing to plan for the future and feeling the spark of inspiration in new music.

CMT: For a lot of these Crossroads collaborations, it seem like a fairly obvious connection. In this case, I don't see it quite so much. Gosh, you guys were on the road and having hits before Luke was born. Did you even know about Luke prior to this?

Tom Johnston: I did not. I'm not gonna sit here and lie to you. But once I was turned on to his music, I really dug it. I was telling Luke, he's got a very unique voice and a very unique delivery. The way he sings and the songs that he writes, as well. It's not like anything I've heard in country before. It's got this rhythmical thing happening to it, and I'm a rhythmical kind of guy so naturally I said, "Yeah, I like that. That's cool."

Luke Bryan: I'm familiar with their music and it was something that I didn't necessarily have to rehearse. But these guys have had their work cut out for them to come in and really dive into my music. It's been so humbling knowing how much they have been working because I had to learn two new songs of theirs, and that was a task for me. And, man, these guys had to learn all four of mine. It's just really, really flattering that they dove in there.

Were you surprised to hear how much of a rock influence Luke has even though he is obviously country?

Pat Simmons: I had listened to his records, and the stuff we are actually performing is pretty rocking material, so I wasn't surprised that it was going to work well. We had to brush up on our country chops. But I'm kind of an old bluegrass guy, and so I'm finding my little bluegrass stuff to throw in here and there. It's just plain fun for us.

What is the most fun aspect of doing a show like this?

Johnston: Having never done one before, I'm digging it. It's fun to get up and play somebody else's stuff. We were talking about this a while ago. It takes you out of your comfort zone. It's something new.

Bryan: It's kind of a crash course in each other's music. You get out of your comfort zone, but that's what makes you nervous again and excited again. That's what gives you a few butterflies.

Simmons: It's fun to be on the edge.

Bryan: Exactly.

Simmons: We never take it for granted. ... This is our 40th anniversary. And so having this puts us back on that edge, back to the beginning. To me, that's what you crave as a musician.

Could you guys have imagined in 1975 that you would be sitting here preparing to go on CMT and play a joint show with a country artist?

Simmons: No, we were thinking about Don Kirshner and The Midnight Special back then.

Johnston: I think that's the other question, "Did you see yourself still doing anything musically down the line in 1975?" Personally, I don't get out of today. I'm right here, right now. That's where it is. Whatever is gonna happen two years from now is beyond me.

Bryan: I think that's what's cool about these guys. I don't think you should plan that. ... People ask me all the time, "Who would you collaborate with?" I'm like, "I don't know. It just depends on what." This came our way, and we're having a damn blast with it. I will forever log this into the ol' memory file. It's really one of the coolest things I've gotten to be a part of.

Luke, when you heard you were going to do this and you're thinking, "Boy, this is great," was there a little bit of intimidation at the beginning?

Bryan: Oh, 1,000 percent. We found out we were gonna do this two weeks ago, and we would sit up and drink coffee in the morning and just practice Doobie Brothers songs. But, man, I got onstage and they might as well have put a dulcimer in my hand when I had my guitar. I was really baffled at how I couldn't even get "Long Train Runnin'." I relaxed and started playing all the chords right, but it's pretty amazing to be up there with guys who are iconic musicians and singers. It was very intimidating.

Is there any one song that you felt, "This is the one that I'm really enjoying"?

Bryan: For me, it's just the fact that I'm even up there playing iconic rock songs with these guys. Tom referenced "Rain Is a Good Thing." That was pretty fun.

Simmons: I have to say that is probably one of the most fun.

Johnston: Well, "Country Girl (Shake It for Me)," I gotta tell you, that's a challenge, but I dig it. I just really try to nail my little singing parts on that thing. He's got more words in the shortest span of time, and that's why I said it sounds like he's been listening to Otis Redding or something. But it's a kick in the ass to go out there and try and get that.