1. Key Designation:
The first symbol in a key signature indicates the key in which the piece is written. For example, a key signature with one sharp (#) indicates the key of G major or E minor, while a key signature with two flats (♭♭) indicates the key of B flat major or G minor.
2. Number of Sharps or Flats:
The number of sharps or flats in a key signature corresponds to the number of notes that are raised or lowered by half a tone (semitone) in that particular scale. Each sharp raises a specific note by one semitone, while each flat lowers a note by one semitone.
3. Order of Sharps and Flats:
The order of sharps and flats in a key signature follows a specific pattern. The sharps are arranged in the order of F-C-G-D-A-E-B, and the flats are arranged in the reverse order of B-E-A-D-G-C-F.
4. Key Signature and Accidentals:
The key signature affects all notes within the piece that match the altered notes indicated by sharps or flats. However, individual accidentals (臨時記号) can override the key signature, indicating that a specific note should be played sharp or flat even if it's not part of the key signature.
5. Major and Minor Keys:
The key signature provides an indication of the major or minor tonality of the piece. Major keys have no flats or sharps in the key signature or use only sharps, while minor keys have at least one flat in the key signature.
Understanding key signatures is essential for reading, playing, and writing music. It helps musicians interpret the correct pitches and tonal relationships within a composition and establishes the tonal center around which the music revolves.