Song Key, Harp Key Tuning
Because diatonic harmonicas are designed to be centered around one major scale, you can't use the same instrument to play in every key like you can with a chromatic harmonica. This means two things: you'll eventually need to have more than one harmonica — in fact, more like seven harmonicas — if you want to have the ability to play in many different keys with other musicians, and you'll need to know which harmonica to select to play in any given key.
Choosing the right key harmonica when playing with others depends on both the song you want to play and the style in which you choose to play it. A folk-style or western traditional song would require you to play a basic melody in the same key as the harmonica, so you would choose a harp that's in the same key as the song you want to play and then play the melody in first position, which will be discussed further below. You may have noticed that the examples and the songs used so far in this book are all in the key of C and are meant to be played using straight harp, or first position.
Matthias Hohner, a German clock maker, turned his full attention to the manufacturing of harmonicas in 1857, producing a total of 650 instruments that year. Thirty years later the Hohner Company was producing over a million harmonicas per year, and today they make over ninety different models of harps.
A blues song or rock and roll song would most likely require you to play in second position, also known as cross harp. For that you must choose a harp tuned to the key three notes above the key of the song. For example, for a song in the key of G you would select a C harmonica and then play in second position.
Here's a quick reference about the correct harp for the key when playing cross harp:
Any song that's in a minor key would require you to play in third position, also known as draw harp, and once again you would need a harmonica that's in a different key than the key of the song. For example, if a song is in D minor you would again use the C harmonica, but this time you would play in third position.
Here's a quick reference about the correct harp for the minor key when playing in third position: