Kat, I have to say I like all of those recordings you listed in your last paragraph. Robeson and Marion Anderson (and Jessye Norman and Kathleen Battle) have concert recordings of spritituals that are absolutely thrilling. Another excellent recording is the first volume of the Smithsonian/Folkways Wade in the Water Series, "African American Spirituals: The Concert Tradition." The whole collection is good - some of the best of the recordings presented by Bernice Johnson Reagon on her "Wade in the Water" series on National Public Redio.
I haven't heard Kiri Te Kanawa singing "Good Night Irene," but she does great work on the songs of Gershwin and Irving Berlin. I imagine I'd like her recording of "Irene."
The Steeleye Span recording of "Rave On" is good - but it ain't traditional, and it certainly ain't Buddy Holly. Buddy Holly's songs are certainly classics that will live for generations, but they certainly aren't the style that we call "traditional." There is one thing about all these recordings that's different from "traditional" music - they're identified with individual performers, and not the music of a community.
-Joe Offer-