Imagine Dolly Parton, Willie Nelson and Kris Kristofferson all sitting in a room together while socializing and writing songs with no clue they're tossing out lyrics and melodies that will forever shape country music history.

For Parton, that's what it was like back in the day, when she and Nelson were fresh on the scene and as green as could be.

"Willie and I came to town about the same time," Parton said recently in Nashville while talking to reporters about her new album, Blue Smoke. "Back in 1964, '65, '66, we both were writing for Combine Music. ... And we used to hang out a lot together, different people. Even Kristofferson back in those days! We all knew each other, and we used to sit around and write different songs."

And whoever popped in to say hello often stuck around to be part of the hang and to visit with friends.

"Whether we were writing together or separately, it was one of those places where everybody kind of flopped down there in the basement of Monument Records, and everybody's kind of hanging around," she said. "So I got to know them, and they got to know me."

Parton added, "Willie and I are so similar. ... I've known him all the days I've been in Nashville, and I just love him."

That love and admiration is mutual. Blue Smoke features Parton and Nelson's recording of "From Here to the Moon and Back," a track they first recorded for Nelson's To All the Girls duets album in 2013.

"I think he's a character, and when we got ready to do the song, Willie called me," she said. "He was doing his album, All the Girls He'd Loved Before or Made Love To, I don't know. ... I was one of the girls he loved. We never had a thing going. It's a wonder, though."

If the love affair didn't happen, the friendship remains strong.

"He said, 'I wanna do duets with all the great gals that I love, and I love your song "From Here to the Moon and Back,"' which is a song I had written for (the film) Joyful Noise," Parton said. "And so he said, 'I can really play the hell out of the guitar on that particular song.' So I said, 'Well, let's go for it!'"

Even though Parton probably knows as much about Nelson's singing as anyone, recording with him is a challenge that many other vocal giants have noted.

"Singing with him was the hardest job I've ever had in my life because we both phrase differently," she said. "And you would think though that because we are both so unusual in our style, that we would just really blend. I mean it worked me to death! Now he'd already put his vocal down, and so I was trying to sing to it.

"I called him up and said, 'Willie, you should have sent me a sack of dope if you thought I was gonna keep up with you!' ... Anyway, we finally did it. I never did quite catch him, but I think the blend of it worked out really well."