In the realm of musical notation, a Key Signature serves as a concise representation of the sharps or flats present in a major or its corresponding natural minor scale. Typically located immediately after the clef at the beginning of a musical staff, key signatures can also appear at other points in a score, particularly following a double barline.

While it is possible to construct key signatures using various combinations of sharp (♯) and flat (♭) symbols, the most commonly encountered ones consist of approximately a dozen diatonic key signatures. These widely used key signatures are assumed in much of the musical repertoire. When a piece is scored using a single diatonic key signature without any accidentals, it encompasses notes from a maximum of seven of the twelve pitch classes. The particular seven pitch classes employed are determined by the specific key signature in use.

In this LESSONSeries , we delve into the intricacies of each major and relative minor key, exploring their primary and secondary chords, as well as providing examples of common chord progressions associated with each key. By mastering these concepts, you will gain a comprehensive understanding of key signatures and their role in music theory and composition.