What does a key signature indicate?

A key signature serves as a crucial element in music notation, providing guidance on which notes will be consistently sharp or flat throughout a piece. It is located at the beginning of a staff and uses specific symbols to indicate these alterations. This means that, unless otherwise indicated, musicians will apply these sharps or flats to all corresponding notes throughout the composition, thereby establishing the tonal center and framework for the piece.

Understanding key signatures is essential because they directly influence the harmonic structure and melodic choices in the music. This element is fundamental to interpreting and performing a piece correctly, as it sets the mood and character of the music. In contrast to other aspects like tempo, dynamics, and time signatures, which relate to the performance style or rhythm, the key signature is specifically about the pitch alterations needed for accurate note execution.