Miranda LambertWhile putting together tapes of songs she would be recording for her album, 'Revolution,' Miranda Lambert enlisted the help of boyfriend Blake Shelton. Up until then, the two had been trying to keep their careers separate from their personal relationship ... but on this day at her place, Miranda couldn't help but feel captivated by something Blake was doing in the background of one of the songs he was working on for her.

"He did this work tape for me, and he was playing guitar for me on my computer," Miranda tells CMT. "He started singing in the background, humming. And I thought it sounded really cool!"

So cool, Miranda just up and asked Blake if he would do what he just did on her record.

"We like to collaborate in an unconventional way, because we're so different, and we really want to keep our careers separate," Miranda points out. "But since we worked together on this record, I thought it'd be cool to have him somewhere. He sang on 'Maintain the Pain' ... he's screaming in the background in the very end!"

The two of them have also done some writing together, but have discovered it only works for them if it happens unexpectedly.

"We've tried [to schedule time to write] before, and it didn't work," says Miranda. "If we schedule it, we normally don't end up doing it. But if it happens organically, it usually ends up good. He'll just be sitting there playing the guitar -- or I will -- and it will lead into a songwriting session. He has a bunch of guitars, and I have one at my house. So there's always one leaning in a corner, somewhere."

Apparently, Miranda also has a bunch of songs she's written, stashed in a corner somewhere ...but she didn't stash them there for herself.

"There are some songs that other people wrote that took the place of mine on this record ... and there were a few songs that I wrote by myself, but just weren't as good as 'The House That Built Me' or 'Time to Get a Gun," she says. "I'd love to write for other people. I have a lot of songs that I don't necessarily want to cut myself, that just aren't for my records ... but that I really want other artists to cut."

As for how she hopes to make that happen?

"I don't know ... it hasn't happened for me yet," she laughs. "When it does, I'll let you know."