"Hi, my name is Marcus Milius. I play harmonica. I got a degree at the University of Southern California, a Bachelor's of Music, in Jazz Studies - Chromatic Harmonica. I play and teach harmonica here in New York City, and I'm happy to show you what I do.
Playing in a key of A is just as simplest of playing in a key of C or any other key you simply need the crack harmonica. So there are 12 different keys in music, there are 12 different harmonicas, each key to different key, rather each tune to a different key.
So you need to make sure that you buy an A harmonica to play in the key of A and any where that you play on that harmonica you will be in the key of A, the harmonicas transpose for you. So any song you learned in the key of C will now be in the key of A, so if you learned to play the Susana in the key of C you will be now in the key of A and you will play it in the same way.
And if you are going to be play with a recording you need to make sure that the recordings in the key of A. If you are in the key of A and the band is playing in the key of F, it's going to sound out of key. It does get more complex so for instance you can play in 12 different keys on any harmonica but the easiest thing to do is playing in what called first position, playing in the key of harmonica."