What does the term 'key signature' indicate?

The term 'key signature' refers specifically to the set of sharps or flats placed at the beginning of a musical staff, which indicates the key of a piece of music. This key determines the scale used and helps musicians identify which notes should be played as sharp or flat throughout the piece. By establishing the tonality, the key signature provides essential information necessary for interpreting the music correctly and helps performers understand the harmonic structure underlying the composition. Understanding the key signature is fundamental for musicians as it informs them how to manage accidentals and contributes to the overall sound and feel of the piece.