Alicia Keys says in an online-exclusive clip from The Voice that her 2004 hit "If I Ain't Got You" — which earned her a Grammy — is one of her "favorite songs ever." Still, the tune isn't rooted in the same type of warmth.

Keys says above that the song, perhaps her most famous, came to be after she found out Aaliyah died. News of the responsible 2001 plane crash really hit Keys hard, she notes, and at least temporarily shifted her focus.

"I actually wrote it right after I heard that Aaliyah passed away, and I was on a plane, and I think being on a plane and knowing she passed away after a plane crash, there was just this sentiment of being present in the moment and really nothing else mattering but those that you love," she explains. "I think that feeling was really present in my life at that time and really right in my face."

And while the story and music manifested without complication, Keys admits landing on a finished version was no easy feat.

"I wrote it really quickly, but in order to produce it the way that you hear it, it took forever," she said. "Nothing would come out right. Every version that I did, every arrangement that I did was just wrong. It was such a labor of love."

Still, it was worth the effort, Keys notes — she says she's surprised the song is still so resonant more than a decade after its release.

"It's definitely one of my favorite songs, and I know a lot of people love that song, and a lot of people have even sung it on the show which I super, super love," she says.

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