It made anything it was added to infinitely better.
Listening to Kenny Loggins and Stevie singing "Whenever I call you friend" and hot damn...he's got a great voice - haven't loved everything he done, but enough - but she just kicks it up a notch. Helps that there must have been some good studio players on this cut. The bass is really nice.
And don't even get me started on Stevie and Lindsey Buckingham. He seems like a dick to me, but the dude can flat out play...and those 2 mixed....it's unreal. Even a few years ago, with her voice really pretty shot she did that duet with him..."Landslide", just her voice and his guitar and it still gave me chills (at least the first few thousand times I heard it). Some people just have to be on frequencies that just mix right. Ian Astbury and Billy Duffy. Meatloaf and Jim Steinman. Paul Simon and Art Garfunkel...c'mon, I know there's more, help me out here.