An easy to play, affordable model. Key of C. The reeds of Diatonic Harmonicas produce the notes of the scale to which they are tuned. For example, a diatonic harmonica tuned to the key of C would produce the natural notes of the C scale without sharps and flats (picture the white keys on a piano, without the black keys). Each hole has two reeds; one plays when breath is exhaled (blow) and the other when inhaled (draw). The individual reeds are each tuned to play a different note on the scale.