Theres more than one way to play a harmonica. The term positions refers to techniques in which different notes form the root of the scale you are using. In this way you can play in several different keys using a harmonica tuned to only one key. And if you are someone like the virtuoso Howard Levy, you can play in all 12 keys of the chromatic scale using a single Richter diatonic harmonica.
Straight and Crossed
The two main positions are straight, where you play in the key that the harmonica is tuned to, and crossed, where you play a harp tuned a fourth above - or, indeed, a fifth below - the key of the song you are playing. Crossed is the standard blues position.
So for example, when you are playing a blues in E (which you often will be) you will need an A harp. For A youll need a D, for G youll need a C and so on.
In straight position, the root note of the scale on a standard Richter diatonic is the blow on the first hole. For crossed, the root is the draw on the second hole.
You can also explore third and fourth positions, which are both good for playing in minor keys. The following chart shows you which harp to use for which position, and where the root notes are:
|Root: Blow 1|
|Root: Draw 2|
|Root: Draw 1|
|Root: Blow 2|