David's Tip of the Day: 4-Point Hold on Harmonica = Less Fatigue, Part 2
The basic 2-Point Hold has the position of the forefinger (A) on the top and thumb (B) on the bottom, but there's nothing stopping the harmonica from pushing away from your mouth as you play. In today's picture note that the middle finger (C) is behind the harmonica, between the comb and upper cover plate. This gives you a 3-Point Hold, making for a more secure harmonica and relaxed holding hand.
Remember to play with a light touch on the face of the harmonica with your mouth and tongue. Excessive force is not only bad for tone and performance of technique, it requires that you unnecessarily grip your harmonica too tightly, often resulting in crushed reed plates.
If you have large hands, create more of a C shape with your left hand, curling your fingers and thumb a tad to make room for your right hand when it comes time to play with both hands on the wheel.
P.S., the finger doesn't effect tone being back there... just in case you were wondering :-)