With regard to steering Elizabeth towards tongue blocking, it was posted:
Sonny Terry: The Folkways Years (all issues)
You'll know the meaning of Tongue Blocking. <snip>
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All due respect, but Sonny Terry did not tongue block - he was a
pucker player. The CD mentioned here IS brilliant, of course -- one
of the greatest of all blues harp recordings! -- but it is not
demonstrative (nor indicative) of tongue blocking. I would instead
recommend instead either Big Walter or Little Walter.