Key (music)

In music theory, the key of a piece is the group of pitches, or scale, that forms the basis of a musical composition in Western classical music, jazz music, art music, and pop music.

A particular key features a tonic (main) note and its corresponding chords, also called a tonic or tonic chord, which provides a subjective sense of arrival and rest. The tonic also has a unique relationship to the other pitches of the same key, their corresponding chords, and pitches and chords outside the key.<ref>Template:Cite web</ref> 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 mode, minor mode, or one of several other modes. Musicians assume major when this is not specified; for example, "this piece is in C" implies that the key of the piece is C major. Popular songs and classical music from the common practice period are usually in a single key; longer pieces in the classical repertoire may have sections in contrasting keys. Key changes within a section or movement are known as modulation.

Background

Music is made from audible vibrations, such as from oscillating strings or air moving through reeds.Template:Sfn. Humans generally perceive some vibrations as sounding "higher" or "lower" than others, creating a subjective perception called pitch.Template:Sfn As a medium vibrates faster, its higher frequency is perceived as higher pitch.Template:Sfn In Western tonal music, specific frequencies are grouped into twelve pitch classes. Seven of these are considered "natural" pitches, and are represented by the letters A, B, C, D, E, F, and G.Template:SfnTemplate:Sfn

Humans perceive frequencies logarithmically, not linearly. The ratio between two frequencies determines how different they sound.Template:Sfn If one vibration has twice the frequency of another, they sound similar enough to be considered the same pitch class; they are said to be one octave apart.Template:SfnTemplate:SfnTemplate:Sfn Pitches separated by an octave are sometimes given numbers to reduce ambiguity. For example, the lowest C playable on a standard piano is designated C1, while the pitch with twice the frequency (one octave higher) is C2.Template:SfnTemplate:Efn

On a piano, the seven natural pitches are played with white keys. The black keys play intermediate pitches which are notated with the symbols ♯ and ♭. The musical distance between adjacent keys is one semitone. A Major Scale begins and ends on a starting pitch, called the Tonic, and follows a pattern of semitone and whole tone steps. In this diagram, the dots represent the seven pitches of the Major scale starting from A, the basis for the key of A Major.

On a piano, each white key represents one of the seven "natural" pitches. These are arranged from A to G, followed by another A one octave higher. Among these pitches, the relative increases in frequency from B to C and from E to F are smaller than the changes between other adjacent pitches. This smaller distance is called a semitone, while the larger distance from e.g. A to B is a whole tone. When two natural pitches are a whole tone apart, a black key represents an intermediate pitch. Instead of using separate letters, these pitches are denoted with the accidentals ♯ (sharp) and ♭ (flat), which represent raising or lowering a natural pitch by one semitone. The pitch between G and A may be denoted as either G♯ (G plus one semitone) or A♭ (A minus one semitone). In musical terminology, G♯ and A♭ are considered enharmonic.Template:Sfn

Most Western music is built around major and minor scales. These scales use seven of the twelve pitches, arranged in ascending or descending order, and beginning and ending with the same pitch one octave apart.Template:SfnTemplate:SfnTemplate:Sfn An ascending major scale moves between pitches with the pattern tone, tone, semitone, tone, tone, tone, semitone.Template:SfnTemplate:SfnTemplate:Efn An ascending minor scale instead uses the pattern tone, semitone, tone, tone, semitone, tone, tone; this results in the third, sixth, and seventh pitches being one semitone lower compared to the major scale.Template:Sfn. On a piano, a major scale beginning from C and a minor scale beginning from A each contain only natural pitches and use exclusively white keys; the two scales are considered distinct "modes" of the same group of pitches.Template:SfnTemplate:Sfn In contrast, a major scale beginning from A uses the pitches A, B, C♯, D, E, F♯, G♯, A.Template:SfnTemplate:Efn The pitch which begins and ends a given scale is called its tonic.Template:Sfn

Definition

A key is a way to classify a piece of music. It represents that the piece is oriented around a specific Major or Minor scale.Template:Sfn The name of a key, such as A Major, contains both a Tonic pitch and a Mode (either Major or Minor). Because there are 12 pitches to use as a tonic, there are 24 distinct keys.Template:SfnTemplate:Sfn Template:Efn If the mode is not specified, the simplified term "key of C" usually implies the key is C Major.Template:Sfn

If a piece of music is in a key, it mostly uses pitches from the corresponding scale.Template:Sfn The seven pitches that belong to the scale are called diatonic pitches, while the remaining five are called chromatic pitches.Template:Sfn A key does not prohibit the use of chromatic pitches, but they will be rarer than diatonic pitches.Template:Sfn The key's tonic represents a pitch of "stability" for the music to orient around. In particular, a composition almost always ends on the tonic.Template:SfnTemplate:Sfn

Not all music has a well defined key. Some classical compositions, such as Chopin's Prelude op. 28 no. 2 and Wagner's Tristan und Isolde, do not clearly follow these patterns.Template:Sfn Modern atonal music, including the works of Arnold Schoenberg, has no tonal stability and freely interweaves all twelve pitches.Template:SfnTemplate:Sfn

Notation

Music is written using a staff (music) with five or more parallel lines. Pitches are represented by notes placed either on a line or in the space between lines. The relationship between pitch and position is defined by a symbol called a clef. In a standard staff with a treble clef, the bottom line represents the pitch E, the line above represents G, and the space between the two lines is F. The pitch between F and G cannot be represented solely by position, so it is represented by marking either an F or G note with an accidental (♯ or ♭).Template:Sfn

In the keys of C Major and A Minor, the common diatonic pitches do not use accidentals.Template:Sfn When writing in other keys, the positions themselves can be marked with accidentals as a shorthand. For example, a ♯ accidental on a line or space representing F means that, unless otherwise specified, all F pitches should be raised one semitone.Template:SfnTemplate:SfnTemplate:Sfn. Another accidental, ♮ (natural), overrides this general rule and represents the natural pitch.Template:SfnTemplate:Sfn When writing this shorthand notation, known as a key signature, Sharps are always arranged in the order F, C, G, D, A, E, B, while Flats use the opposite order.Template:Sfn

A key signature allows the corresponding major or minor scale to be written without accidentals.Template:SfnTemplate:Sfn Any remaining accidentals represent chromatic pitches which are less closely associated with the key.Template:Sfn However, a key signature does not uniquely specify a key, since it does not identify the tonic. Any key signature could represent either a major or minor key with the same pitches but different tonics.Template:SfnTemplate:Sfn

Modulation

Short pieces may stay in a single key throughout. A typical pattern for a simple song might be as follows: a phrase ends with a cadence on the tonic, a second phrase ends with a half cadence, then a final, longer, phrase ends with an authentic cadence on the tonic.

More elaborate pieces may establish the main key, then modulate to another key, or a series of keys, then back to the original key. In the Baroque it was common to repeat an entire phrase of music, called a ritornello, in each key once it was established. In Classical sonata form, the second key was typically marked with a contrasting theme. Another key may be treated as a temporary tonic, called tonicization.

In common practice period compositions, and most of the Western popular music of the 20th century, pieces always begin and end in the same key, even if (as in some Romantic-era music) the key is deliberately left ambiguous at first. Some arrangements of popular songs, however, modulate sometime during the song (often in a repeat of the final chorus) and thus end in a different key. This is an example of modulation.

In rock and popular music some pieces change back and forth, or modulate, between two keys. Examples of this include Fleetwood Mac's "Dreams" and The Rolling Stones' "Under My Thumb". "This phenomenon occurs when a feature that allows multiple interpretations of key (usually a diatonic set as pitch source) is accompanied by other, more precise evidence in support of each possible interpretation (such as the use of one note as the root of the initiating harmony and persistent use of another note as pitch of melodic resolution and root of the final harmony of each phrase)."<ref name="Stephenson">Ken Stephenson, What to Listen for in Rock: A Stylistic Analysis (New Haven: Yale University Press, 2002), 48. Template:ISBN.</ref>

Instruments in a key

Certain musical instruments play in a certain key, or have their music written in a certain key. Instruments that do not play in the key of C are known as transposing instruments.<ref>Kent Wheeler Kennan, The Technique of Orchestration, 2nd edition (Englewood Cliffs, New Jersey: Prentice-Hall, 1970), 1952; Template:ISBN.</ref> The most common kind of clarinet, for example, is said to play in the key of BTemplate:Music. This means that a scale written in C major in sheet music actually sounds as a BTemplate:Music major scale when played on the B-flat clarinet—that is, notes sound a whole tone lower than written. Likewise, the horn, normally in the key of F, sounds notes a perfect fifth lower than written.

Similarly, some instruments are "built" in a certain key. For example, a brass instrument built in BTemplate:Music plays a fundamental note of BTemplate:Music, and can play notes in the harmonic series starting on BTemplate:Music without using valves, fingerholes, or slides to alter the length of the vibrating column of air. An instrument built in a certain key often, but not always, uses music written in the same key (see trombone for an exception). However, some instruments, such as the diatonic harmonica and the harp, are in fact designed to play in only one key at a time: accidentals are difficult or impossible to play.

The highland bagpipes are built in BTemplate:Music major, though the music is written in D major with implied accidentals.

In Western musical composition, the key of a piece has important ramifications for its composition:

• As noted earlier, certain instruments are designed for a certain key, as playing in that key can be physically easier or harder. Thus the choice of key can be an important one when composing for an orchestra, as one must take these elements into consideration.
• In the life of the professional clarinetist, for example, it is common to carry two instruments tuned a semitone apart (BTemplate:Music and A) to cope with the needs of composers: Mozart's well-known clarinet concerto is in A major. To play it on a BTemplate:Music instrument is difficult, and to rewrite all the orchestral parts to BTemplate:Music major would be an enormous effort. Even so, it is not unheard of for a piece published in BTemplate:Music to include notes a semitone (or more) below the range of the common BTemplate:Music clarinet. The piece must then be played on a more exotic instrument, or transposed by hand (or at sight) for the slightly larger A clarinet. There are clarinets with an extended range, with a longer bore and additional keys.
• Besides this though, the timbre of almost any instrument is not exactly the same for all notes played on that instrument. For this reason a piece that might be in the key of C might sound or "feel" somewhat different (besides being in a different pitch) to a listener if it is transposed to the key of A.
• In addition, since many composers often utilized the piano while composing, the key chosen can possibly have an effect over the composing. This is because the physical fingering is different for each key, which may lend itself to choosing to play and thus eventually write certain notes or chord progressions compared to others, or this may be done on purpose to make the fingering more efficient if the final piece is intended for piano.
• In music that does not use equal temperament, chords played in different keys are qualitatively different.

Works Cited

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Further reading

• Innig, Renate (1970). System der Funktionsbezeichnung in den Harmonielehren seit Hugo Riemann. Düsseldorf: Gesellschaft zur Förderung der systematischen Musikwissenschaft.
• Rahn, John (1980). Basic Atonal Theory. New York: Longman; London and Toronto: Prentice Hall International. Template:ISBN. Reprinted 1987, New York: Schirmer Books; London: Collier Macmillan.
• Steblin, Rita (1983). A History of Key Characteristics in the 18th and Early 19th Centuries. UMI Research Press, Ann Arbor.

External links

• Christian Schubart's "Affective Key Characteristic"
• Characteristics of Musical Keys – from various sources.
• Key Color
• Historical Tuning – Restoring Key Coloration to Period Music Template:Webarchive