The Hohner Auto Valve features 40 reeds and two separate rows of 10 holes each. Therefore, it can be played as a regular C or high C diatonic. But you also have the option to play both rows of holes at once. If you play it that way, it will produce an interesting sound that has been compared to an organ. Although the sound is quite unique and interesting, this harmonica only comes in the key of C. So, you may be limited as far as which songs you can comfortably play on it. Nevertheless, it does have the advantage of making a lot of sound for very little breath.
Only comes in two keys