This diagram shows the relationship among the (12 tones)Western Chromatic Sale, their corresponding key signatures and their associated Minor an Major keys. It is also very usefull to interpret chord progressions, calculate scales and even for transposing music.

The inner circle corresponds Minor, the outer circle Major

Interactive Circle of Fifths
The Interactive Circle of Fifths is a free online music theory tool designed to help musicians to interpret chord progressions, easily transpose music to a different key, compose new music, and understand key signatures, scales, and modes. It goes beyond the limitations of a traditional, static diagram without sacrificing clarity and simplicity, and it includes an extensive User's Guide to help you discover all that it has to offer.
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