I thought I would share a little about cross harp for harmonica. I don't now a whole lot about music, I've never had any lessons but I will try to explain best I can! When I cross harp if I am playing in the key of (E) like on Minute By Minute I use a harmonica in the key of (A). For a song like Blues in my Soul played in the key of (G) I use a harmonica in the key of (C).
I also never used the technique of tongue blocking that came with my first harp or Mississipi Saxaphone instructions. I first tried to make the sound of a train whistle best I could..then to the right it got higher to the left it went lower and I found most the good notes when I cross harp were found when I was inhaling. I then just try to breathe, blow and inhale with rythm and have fun. Unlike other players who play actual songs and melodies my technique has only been successful to me for playing along with my guitar. HAVE FUN & GOD BLESS!!!!!