Key (music)

In music theory, a key is a tonal system that organizes pitches and chords around a central note called the tonic. It establishes a hierarchical relationship between the tonic and other pitches within the key, creating a sense of resolution and expectation.

The key is determined by the specific arrangement of whole and half steps within its corresponding scale. Major keys are characterized by a bright and cheerful sound, while minor keys often have a darker or more somber quality.

Key signatures, written at the beginning of a musical staff, indicate which notes are consistently sharped or flatted throughout a piece in that key. These sharps or flats define the characteristic intervals of the scale. For example, the key of G major has one sharp (F#), while the key of F major has one flat (Bb).

Modulation is the process of changing from one key to another within a piece of music. This can create contrast and interest, and can be achieved through various harmonic techniques.

The concept of key is fundamental to Western tonal music, providing a framework for melody, harmony, and musical form. Understanding key relationships is essential for analyzing, composing, and performing music. The circle of fifths is a visual representation of key relationships, showing how keys are related by the number of sharps or flats in their key signatures. Related keys share a greater number of common tones and thus allow for smoother modulations.