The kalimba, or mbira, is a very simple instrument which can be easily tuned. Models vary in complexity and tone, but the two BrandNewNoise versions are easy for anyone to start playing immediately reguardless of musical knowledge.
The tines (or keys) on kalimbas are generally made of spring spring steel. To change the pitch you can slide these pieces back or fowards under the square bar holding them in place. You must first loosen the bar, starting with turning the two screws about a 1/4 to a 1/2 turn. You can then easily move the keys with your fingers (I wear a thimble for extra leverage).
The BrandNewNoise Zoots and Hubble both come tuned to notes in the key of C major.
If you wish to purchase an additional set of keys, you can follow the video for how create a chromatic scale.
BrandNewNoise kalimbas have been used on recordings by Death Cab for Cutie, The Lego Movie soundtrack by Mark Mothersbaugh of Devo, and more.