Johnny Mars Plays That Harp Riff

How to play this riff, watch the video The harmonica I used is Lee Oskar, Natural Minor, Model #1910N (Green Label). The music is in G and I play i 2nd position so I should choose a C harp. But this Natural Minor harp has the label Gm instead of C. That´s important to remember if you buy that harp! I don´t know exactly which harp or tuning Johnny Mars uses in this video. I think it´s Hohner Meisterklasse.