A key is determined by the arrangement of notes in a scale and the relationships between them. The notes within a key have different functions, with some acting as tonic, dominant, or subdominant, contributing to the overall harmonic structure of the music.
When a piece is in a particular key, the tonic note serves as the point of resolution and stability. The dominant note creates tension and a sense of movement, while the subdominant note provides contrast and balance. The relationships between these notes and chords establish a framework that guides the melodic and harmonic development of the music.
For example, if a piece is in the key of C major, the notes C, E, and G form the basic triad, and other notes from the C major scale can be used to create melodies, harmonies, and progressions. The key signature at the beginning of a staff indicates which key a piece is in, using sharps or flats to raise or lower certain notes accordingly.
Composers and musicians often choose a specific key for their music based on the desired emotional effect or the suitability for the range and capabilities of particular instruments or voices. Different keys can evoke distinct moods and characteristics, ranging from bright and cheerful to somber and melancholic.
Understanding and recognizing the key of a piece of music is essential for performers and analysts, as it helps in interpreting and executing the music accurately. It provides a roadmap for how the notes and chords relate to each other, allowing musicians to improvise, harmonize, and develop musical ideas within the framework of the chosen key.