In Western tonal music a key is the central aural reference point established by pitch relationships creating a set, in a given musical piece or section. These pitch sets result in an establishment of a major mode or a minor mode which is determined by the relationships of the intervals within a scale and the chords they produce. Adherence to the elements of a major or minor scale and the resultant chords determines the key center of a particular musical composition.
Although the key of a piece may be named in the title (e.g. Symphony in C), 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.
A key may be major or minor. Some music is considered to be in a mode—such as the Dorian or Phrygian mode—rather than a key. When a particular key is being described in a language other than English, different key naming systems may be used.
The chords used within a key are generally drawn from the major or minor scale associated with the tonic triad, but may also include borrowed chords, altered chords, secondary dominants, and the like. All of these chords, however, are used in conventional patterns which serve to establish the primacy of the tonic triad.
Cadences are particularly important in the establishment of key. Even cadences which do not include the tonic triad, such as half cadences and deceptive cadences, serve to establish key because those chord sequences imply a unique diatonic context.
There are seven major sharp keys centers (G, D, A, E, B, F-sharp, C-sharp) and seven major flat key centers (F, B-flat, E-flat, A-flat, D-flat, G-flat, C-flat). There are also the relative minor sharp keys, and relative minor flat keys.
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 period 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 twentieth century—pieces 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, will modulate up a half-step sometime during the song (often in a repeat of the final chorus) and thus will end in a different key.
Certain musical instruments are sometimes said to play in a certain key, or have their music written in a certain key. Instruments which do not play in the key of C are known as transposing instruments. The most common kind of clarinet, for example, is said to play in the key of B flat. This means that a scale written in C major in sheet music will actually sound as a B flat major scale when played; 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 may be said to be built in a certain key. For example, a brass instrument built in B flat will play a fundamental note of B flat, and will be able to play notes in the harmonic series starting on B flat without using valves, fingerholes, or slides or otherwise altering the length of the vibrating column of air. An instrument built in a certain key will often, but not always, have its 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 only one key at a time: accidentals are difficult or impossible to play.
In general string instruments tend to be tuned in sharp keys (such as C, D, A, and E); and wind instruments tend to be tuned to flat keys (such as F, B-flat, and E-flat).
In rare cases, all instruments in the choir will be in the same key, regardless of range. Prior to 2000, for example, in music for a drum and bugle corps, all brass lines were not only in the key of G but all instruments—soprano, alto, baritone, euphonium, and contrabass—were in the treble clef. This made it much easier for arrangers to switch parts around to experiment with different tone colors. However, the drum corps is probably the only musical ensemble with all ranges of instrumentation in the same key and clef.
The key determines the tonality in which the music is played. It can be in either a major or a minor key, or occasionally in a mode rather than a key. In Western musical composition, the key of a song has important ramifications for its composition. As noted earlier, certain instruments are said to be designed for a certain key, as playing in that key can be physically easier, and playing properly in another key may be extremely difficult. Thus the choice of key can be an important one when composing for an orchestra, as one must take these elements into consideration.
Musicians some time make adjustments to deal with the problem of music written in a difficult key. In the life of the professional clarinetist, for example, it is common to carry two instruments tuned a semitone apart (B-flat and A) to cope with the needs of composers: Mozart's well-known clarinet concerto is in A Major. To play it on a B-flat instrument would be difficult, and to rewrite all the orchestral parts to allow the piece to be played in B-flat major would be an enormous effort. Even so, it is not unheard of for a piece published in B-flat to include notes a semitone (or more) below the range of the common B-flat 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. As a last resort, it is also not unheard of for a player to roll up a page of the score and insert it into the end of the instrument in order to lengthen it.
Besides this, the timbre of almost any instrument is not exactly the same for all notes played on that instrument. For this reason a song that might be in the key of C might sound or "feel" somewhat different (besides being in a different pitch) to an observer if it is transposed to the key of A. This effect is more pronounced on instruments like the piano, where certain notes have more strings or a thicker string associated with them.
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. This is especially true of composers who are not piano virtuosi.
French composer and organist Jean-Phillipe Rameau (1683-1764) published his Traité de l'harmonie in 1722 in which he posited that there was a fundamental relationship between the harmonic principles in tonal music and the physics of sound (acoustics.) He asserted that chords where the primary elements in music as opposed to melody or themes in establishing key centers. His ideas regarding functional harmony, specifically the cadential relationship between the tonic, sub-dominant and dominant chords within a particular key center, became the underlying principles of what would become known as “the common practice” in musical composition in the Western music for 300 years. The cadential relationship between tonic and dominant triads (as well as secondary dominants) is elemental to the tonal syntax.
All links retrieved April 16, 2018.
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