Well....it's potentially a lot more than an outline. If you're songwriting for someone, you record the song yourself and send it like, "Here, this is how I picture it sounding," maybe right down to different intonations or phrasings or ad-libs. And then if the artist decides to record that song they "reference" the original version, decide how much of that original they want to change or do their own way.
So the final version could end up sounding almost exactly like the reference version only with a different singer, or it could end up pretty different. Case by case basis.
Lucas [1:14 PM]
Is it different than songwriting?
Nathanslavik [1:16 PM]
No, it's the exact same thing, a reference track is how a songwriter shares their songwriting. Like, if you write a song for someone, what then? You email them the sheet music? You need to let them hear the song you wrote, so you have to record a "reference" version to send. Sometimes that might just be a piano or guitar and the songwriter singing, something stripped down, maybe not even verses, just the hook. Or they could almost literally record the song in full for the reference, bring in strings, multi-instruments, etc. Like PND could have gotten a female singer who sounds like Rihanna to do that reference so it'd be easier for Rihanna to hear herself singing it (and therefore maybe more likely for her to want to record it), that happens all the time.