According to what I heard when asking the ancestral spirits, they said that they heard mbira music coming from a rock in the middle of the ocean. So, when they used to pass by there, they would hear that music sounding. So then they thought, “What kind of instrument could we make that would produce the sound of the music we are hearing?” That is how they came to make the instrument called mbira.
This instrument, the mbira, started as a small karimba, with six keys. So once they had played and played, then they added a seventh key. And as time passed, it developed. It goes together with your singing, as you search for new keys that will support your voice. When you raise your voice, you need another key there. If you sing very low, you’ll search for another key that is also low.
So they kept playing. So as they continued playing, they kept adding more and more keys, until the karimba had fifteen keys. And some people added yet more, until it had nineteen keys.