For you capo users, CapoCalc allows you to calculate the right place to set a capo to match another musician's true key while you play in a different "guitar key". It lets you enter the other person's relative or absolute key, and then computes the proper capo setting for the desired guitar key.
As an example, if you are playing with a fiddler (aka "violinist") who is playing in the key of A, you enter "A" for their key and "0(none)" for their capo setting. Then if you want to play your guitar in the relative key of G, enter that and CapoCalc will tell you where to set your capo. The answer is capo-2, behind the 2nd fret. That one was easy :-).
Suppose you want to play with another guitarist who is playing in the guitar key of C at capo position 2. If you decide you want to play your guitar in the key of G, how do you make this work? In CapoCalc enter "C" for the other person's relative key, "2" for their capo position, and "G" for your desired guitar key. CapoCalc will then tell you the answer: you capo at position 7. You're both playing in the absolute key of D.
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