In this book you have learned to play in two keys – C in first position and G in second position (cross harp). However, many times when you play with other musicians or play along with your favorite albums, other keys will be used.
Once you are comfortable playing the C harmonica it is a good idea to try a few others in different keys. The playing techniques are identical regardless of the key you are playing in, only the actual pitch of the notes change. This means that once you can play a song on the C harmonica, you can transfer it directly to any other harmonica and play the same holes with the same breathing and it will sound just as good.
If you are playing an A harmonica in first position, you will be playing in the key of A major. If you are playing a D harmonica in first position, you will be playing in the key of D major. This means that if you are playing with a guitarist for example, you can easily find the correct key for many songs simply by choosing the harmonica with that key written on it.
For second position or cross harp playing however, it can sometimes be confusing trying to find the right harmonica to fit with what the other musicians are playing. In this situation it becomes more important to know the sounds on the harmonica as scale degrees. E.g., if a guitarist is playing a Blues in E (a common key for Blues), you would use an A harmonica to play cross harp in second position. The notes found at holes 2, 3, 6 and 9 would all be E notes on the A harmonica.
If you know that the notes at these holes are the first degree of any scale in the cross harp position, this makes it easier to understand why the A harmonica is the one chosen for a Blues in E. If you used any other key harmonica, the notes at these holes would not be E and the harmonica would not work for a Blues in E. There are actually more positions you can use on each harmonica, but these are more advanced and are not dealt with here.
The following chart lists all the keys used in music along with the correct harmonica for playing second position cross harp with each key. The easiest way to check if you are using the right harmonica for the key is to play holes 2, 3, or 6 and see if it is the same note as the key you want by testing it against a guitar or keyboard chord. If the guitar plays a D chord, your note should be a D note, if the guitar plays an F chord, your note should be an F note, etc. You can usually tell by ear if you have the correct note or not.