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The latest Gadget Freak shows you how to make a music key display –

There was dissonance in the church when the pianist and other musicians had to hunt for the key their Music Leader was playing in. Dick’s gadget took the guesswork out of the guitar, the meandering out of the mandolin and the pondering out of the piano. The Music Leader communicates the key to the others by setting the display on his Sending Unit via pushbutton or the foot switch, and the Remote Units replicate that display for everyone else. Now, they’re all in one A chord (or F, or C, or…).

HOW TO – Make a music key display – Link.