Joanna: How come the orchestras behind Billie Holiday were so amazingly good?...and she sang like one more instrument among the others ...in some of the purest and best jazz I've ever heard...
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I love her singing also -- but the hairs rise on the back of my neck every time I hear such words as "pure" outside the chemistry lab or in reference to the bacteria count of food supplies. I don't claim that is the only legitimate context for the word, but whenever it is applied outside that context it needs to be defended.
I really doubt that it is applicable to music. Just as I doubt "authenticity" has any business appearing in a commentary on a speech at a political rally. Actuality is never "pure," just as actuality is by definition genuine (authentic) actuality.
Carrol