Thumb in Front of Harmonica (Part 1)

Have you noticed that most pro players hold the harmonica with their left hand and use their right to overlap their left, and specifically the thumb of the right hand to cover 2-3 holes on the high-end? The thumb is an important element of a tight cup to perform the Wa Wa and playing through a bullet mic. Yesterday I stated that sound escapes all around the harmonica, and the upper holes of the harmonica are a big leakage area. Hold the harmonica the way you normally do in front of a mirror... look at how the upper holes are open... tomorrow we'll speak of how pro players deal with that leakage.