Brad Paisley is one of Carrie Underwood's best friends, so it was only a matter of time before the two collaborated on a song. However, the process took longer than both expected. Carrie recently explained just how 'Remind Me' came about and why Brad's 'Waitin' on a Woman' may not be about the person you think.

In Nashville for the Billboard Country Music Summit, Carrie revealed that doing a song together had been on the radar of the two superstars for a while, but she doesn't like to force things. "We're not gonna sing 'Yankee Doodle Dandy' just because we both know it and we need to sing together. We both wanted to do this."

Once Brad pushed back the release date of his album, 'This Is Country Music,' the two were finally able to set up a time to meet.

"Let me tell you something about Brad Paisley," says Carrie. "Brad is not on time. You tell him something's going to happen 30 minutes before so he shows up on time. I've learned this from co-hosting with him. He's a great guy, but he's on 'Paisley Time.' And I always say, 'Waiting on a woman'? Yeah right!'"

Brad may need reminding about keeping his appointments, but Carrie revealed that no one had to 'Remind Me' about when the song was recorded, thanks to her hockey-star hubby and the NHL.

"We recorded it on February 11 because my husband got traded on the 10th, so that's how I know," she explains. "[Brad] calls me up February 9 and says, 'Hey! I have this idea for a song!' I said, 'I thought you were supposed to deliver it already.' He says, 'No, nope. It wasn't ready yet and it got pushed back.'"

Brad had an idea, not a complete song, which was about a couple finding their way back to what used to be. He hummed it to Carrie on speakerphone while she was in her hotel room in L.A. Right away, she saw the song's potential and asked him to send her a work tape so they could figure it out together.

"His son actually had a play date with Sheryl Crow's son and he asks her -- totally puts her on the spot, I'm sure -- to sing the female part. I have this work tape demo with Sheryl Crow singing my part. There's mumbling, a few lines here and there."

Carrie explained that she saw something in the song and flew back to Nashville to work with Brad.

"They were still changing lines," Carrie notes. "It was the most unorganized thing I had ever been a part of. I had never done anything like that before. It all worked out so perfectly. I was so happy. I felt like that was given to us. I was so excited about the song once the words became established and I was so happy he didn't deliver [his album] on time. It kept it in the moment, just doing it off the cuff. It wouldn't have been the same song had we recorded it and recorded it."

'Remind Me' is rapidly climbing the charts and Brad's current single, 'Old Alabama,' is sitting at No. 1.

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