Key (music)

In music theory, the key of a piece is the group of pitches, or scale, that forms the basis of a music composition in classical, Western art, and Western pop music. the key of the piece ... contributes an indefinable something to the evocative quality. This is very difficult to put into concrete terms, but slow movements in A-flat major do have something in common, as do fast movements in C minor, concerto allegros in D major, etc. There has been disagreement on this point. It has been argued, since standards of pitch level have changed over the centuries, that today we actually hear pieces written two centuries ago in a different (usually higher) key than that intended by the composer. It has been argued that the performer's concept of particular key is actually created by factors such as the 'feel' of the key or tonal center on the keyboard or its appearance in notation. Many musicians, however, tend toward an empirical acceptance of specific moods associated with specific keys, regardless of changes in pitch standards and other factors. In music theory, the key of a piece is the group of pitches, or scale, that forms the basis of a music composition in classical, Western art, and Western pop music. The group features a tonic note and its corresponding chords, also called a tonic or tonic chord, which provides a subjective sense of arrival and rest, and also has a unique relationship to the other pitches of the same group, their corresponding chords, and pitches and chords outside the group. Notes and chords other than the tonic in a piece create varying degrees of tension, resolved when the tonic note or chord returns. The key may be in the major or minor mode, though musicians assume major in a statement like, 'This piece is in C.' Popular songs are usually in a key, and so is classical music during the common practice period, around 1650–1900. Longer pieces in the classical repertoire may have sections in contrasting keys. Methods that establish the key for a particular piece can be complicated to explain and vary over music history. However, the chords most often used in a piece in a particular key are those that contain the notes in the corresponding scale, and conventional progressions of these chords, particularly cadences, orient the listener around the tonic. The key signature is not always a reliable guide to the key of a written piece. It does not discriminate between a major key and its relative minor; the piece may modulate to a different key; if the modulation is brief, it may not involve a change of key signature, being indicated instead with accidentals. Occasionally, a piece in a mode such as Mixolydian or Dorian is written with a major or minor key signature appropriate to the tonic, and accidentals throughout the piece. Pieces in modes not corresponding to major or minor keys may sometimes be referred to as being in the key of the tonic. A piece using some other type of harmony, resolving e.g. to A, might be described as 'in A' to indicate that A is the tonal center of the piece. An instrument is 'in a key', an unrelated usage that means the pitches considered 'natural' for that instrument. For example, modern trumpets are usually in the key of B♭, since the notes produced without using the valves correspond to the harmonic series whose fundamental pitch is B♭. (Such instruments are called transposing when their written notes differ from concert pitch.) A key relationship is the relationship between keys, measured by common tone and nearness on the circle of fifths. See closely related key. The key usually identifies the tonic note and/or chord: the note and/or major or minor triad that represents the final point of rest for a piece, or the focal point of a section. Though the key of a piece may be named in the title (e.g., Symphony in C major), or inferred from the key signature, the establishment of key is brought about via functional harmony, a sequence of chords leading to one or more cadences, and/or melodic motion (such as movement from the leading-tone to the tonic). For example, the key of G includes the following pitches: G, A, B, C, D, E, and F♯; and its corresponding tonic chord is G—B—D. Most often at the beginning and end of traditional pieces during the common practice period, the tonic, sometimes with its corresponding tonic chord, begins and ends a piece in a designated key. A key may be major or minor. Music can be described as being in the Dorian mode, or Phrygian, etc., and is thus usually thought of as in a specific mode rather than a key. Languages other than English may use other key naming systems.