Deep relaxed mouth position and semi-pucker technique pushes harmonica back - Technique - Harmonica Forum
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Amazon.com: How To Play The Harmonica: A Beginners Guide to Learn How To Play The Harmonica (Woodwinds for Beginners): 9781549709050: Randall, Jason: Books
Tongue blocking vs puckering - C harmonica lesson for beginners - YouTube
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Tongue Blocking VS Puckering for Playing Single Notes (Harmonica Lesson) - YouTube