Music theory

Music theory is the field of study that deals with how music works. It examines the language and notation of music. It identifies patterns that govern composers' techniques. In a grand sense, music theory distills and analyzes the parameters or elements of music – rhythm, harmony (harmonic function), melody, structure, form, and texture. Broadly, music theory may include any statement, belief, or conception of or about music [1]. People who study these properties are known as music theorists. Some have applied acoustics, human physiology, and psychology to the explanation of how and why music is perceived.

Elements of music
Music has many different elements. The main elements are: rhythm, melody, harmony, structure, timbre, dynamics, and texture. Each element—and each of its sub-elements, if any—is discussed below.

Melody
A melody is a series of notes sounding in succession. The notes of a melody are typically created with respect to pitch systems such as scales or modes. The rhythm of a melody is often based on the inflections of language, the physical rhythms of dance, or simply periodic pulsation. Melody is typically divided into phrases within a larger overarching structure. The elements of a melody are pitch, duration, dynamics, and timbre.
In the context of theory, a piece of music may be melodically based. In this instance, a composer will first take a melody, and use that to create his or her work. A harmonically based piece, on the contrary, will focus on a chord progression, with the melody as a secondary or incidental factor of composition.

Pitch
Pitch is a subjective sensation, reflecting generally the lowness or highness of a sound. In a musical context, some people have what is called perfect pitch and can assign an isolated tone to its place on a musical scale. Human perception of pitch can be comprehensively fooled to create auditory illusions. Such effects have been occasionally exploited in music from artists such as Johann Sebastian Bach and Pink Floyd. Despite these perceptual oddities, perceived pitch is nearly always closely connected with the fundamental frequency of a note, with a lesser connection to sound pressure level, and to the immediately preceding history of notes heard. Higher pitch generally corresponds to higher frequency and lower pitch to lower.
At and below about 1,000 Hz, the perceived pitch of a tone gets lower as sound pressure increases, but above approximately 2,000 Hz, the pitch increases as the sound gets louder.[2]
In Western music, there have long been several competing pitch standards defining tuning systems. Most made a particular key sonorous, with increasingly remote ones more and more problematic; the underlying problem is related to the physics of vibrations. Bach participated in these controversies with his extensive exploration of the Well Tempered Clavier which demonstrated the inevitable musical difficulties which attend any but a choice of equal temperament tuning.
In addition, fixing any particular note's frequency (required for a standard to which instrument makers could repair) has varied as well. "Concert A" was set at 435 Hz by France in 1859 while in England, concert A varied between 439 and 452 Hz. A frequency of 440 Hz was recommended as the standard in 1939, and in 1955 the International Organization for Standardization affirmed the choice.[3] A440 is now widely, though not exclusively, used as the A above middle C.
The difference in frequency between two pitches is called an interval. The most basic interval is the octave, which indicates either a doubling or halving of the fundamental frequency.

Scales and modes
Main articles: Musical scale and Musical mode
Notes can be arranged into different scales and modes. Western music theory generally divides the octave into a series of 12 notes that might be included in a piece of music. This series of twelve notes is called a chromatic scale. In the chromatic scale, each note is called a half-step or semitone. Patterns of half and whole steps (2 half steps, or a tone) can make up a scale in that octave. The scales most commonly encountered are the seven toned major, the harmonic minor, the melodic minor, and the natural minor. Other examples of scales used are the octatonic scale, and the pentatonic or five-toned scale which is common in but not limited to folk musics. There are scales that do not follow the chromatic 12-note pattern, for example in classical Persian, Indian and Arabic music. Arabic and Persian classical traditions often make use of quarter-tones, half the size of a semitone, as the name suggests. Contrary to popular belief, however, this is not true of Indian music, which uses 7 notes and 5 variant notes that correspond to the 12 tones of the European chromatic scale, but are used very differently. Theoretically the 12 tones of Indian music map onto a 22 division of the octave according to the thirteenth-century Sanskrit treatise, the Sangitaratnakara.
In music written using the system of major-minor tonality, the key of a piece determines the scale used. (One way of showing how various keys relate to one another may be seen in the circle of fifths.) Transposing a piece from C major to D major will make all the notes two semitones (or one full step) higher. Even in modern equal temperament, changing the key can change the feel of a piece of music, because it changes the relationship of the composition's pitches to the pitch range of the instruments on which the piece is being performed. This often affects the music's timbre, as well as having technical implications for the performers. However, performing a piece in one key rather than another may go unrecognized by the casual listener, since changing the key does not change the relationship of the individual pitches to each other. A key change, or modulation, may occur during a piece, which is more easily heard as a difference of intervals in sound.

Rhythm
Main article: Rhythm
Rhythm is the arrangement of sounds and silences in time. Meter animates time in regular pulse groupings, called measures or bars. The time signature or meter signature specifies how many beats are in a measure, and which value of written note is counted and felt as a single beat. Through increased stress and attack (and subtle variations in duration), particular tones may be accented. There are conventions in most musical traditions for a regular and hierarchical accentuation of beats to reinforce the meter. Syncopated rhythms are rhythms that accent unexpected parts of the beat. Playing simultaneous rhythms in more than one time signature is called polymeter. See also polyrhythm.
In recent years, rhythm and meter have become an important area of research among music scholars. Recent work in these areas includes books by Bengt-Olov Palmqvist, Fred Lerdahl and Ray Jackendoff, Jonathan Kramer, Christopher Hasty, William Rothstein, and Joel Lester.

Harmony
Main article: Harmony
Harmony is the study of vertical sonorities in music. Vertical sonority refers to considering the relationships between pitches that occur together; usually this means at the same time, although harmony can also be implied by a melody that outlines a harmonic structure.
The vertical relationship between two pitches is referred to as an interval. A larger structure involving multiple pitches is called a chord. In Common practice and Popular music, harmonies are generally tertian. This means that the interval of which the chords are composed is a third. Therefore, a root-position triad (with the root note in the lowest voice) consists of the root note, a note a third above, and a note a third above that (a fifth above the root). Seventh chords add a third above the top note of a triad (a seventh above the root). There are some notable exceptions. In 20th century classical music, many alternative types of harmonic structure were explored. One way to analyze harmony in Common practice music is through a roman numeral system; in Popular Music and Jazz a system of chord symbols is used; and in post-tonal music, a variety of approaches are used, most frequently set theory.
The perception of pitch within harmony depends on a number of factors including the interaction of frequencies within the harmony and the roughness produced by the fast beating of nearby partials. Pitch perception is also affected by familiarity of the listener with the music, and cultural associations.

Consonance and dissonance
Main article: Consonance and Dissonance
Consonance can be roughly defined as harmonies whose tones complement and increase each others' resonance, and dissonance as those which create more complex acoustical interactions (called 'beats'). A simplistic example is that of "pleasant" sounds versus "unpleasant" ones. Another manner of thinking about the relationship regards stability; dissonant harmonies are sometimes considered to be unstable and to "want to move" or "resolve" toward consonance. However, this is not to say that dissonance is undesirable. A composition made entirely of consonant harmonies may be pleasing to the ear and yet boring because there are no instabilities to be resolved.
Melody is often organized so as to interact with changing harmonies (sometimes called a chord progression) that accompany it, setting up consonance and dissonance. The art of melody writing depends heavily upon the choices of tones for their nonharmonic or harmonic character.
"Harmony" as used by music theorists can refer to any kind of simultaneity without a value judgement, in contrast with a more common usage of "in harmony" or "harmonious", which in technical language might be described as consonance.

Dynamics
Main article: Dynamics (music)
In music, dynamics normally refers to the softness or loudness of a sound or note, e.g. pianissimo or fortissimo. Until recently, most of these dynamics and signs were written in Italian, but recently are becoming written or translated into English. However, to every aspect of the execution of a given piece, either stylistic (staccato, legato etc.) or functional (velocity) are also known as dynamics. The term is also applied to the written or printed musical notation used to indicate dynamics.

Texture
Main article: Musical texture
Musical texture is the overall sound of a piece of music commonly described according to the number of and relationship between parts or lines of music: monophony, heterophony, polyphony, homophony, or monody. The perceived texture of a piece may also be affected by the timbre of the instruments, the number of instruments used, and the interval between each musical line, among other things.
Monophony is the texture of a melody heard only by itself. If a melody is accompanied by chords, the texture is homophony. In homophony, the melody is usually but not always voiced in the highest notes. A third texture, called polyphony, consists of several simultaneous melodies of equal importance.

Form or structure
Main article: Musical form
Form is a facet of music theory that explores the concept of musical syntax, on a local and global level. The syntax is often explained in terms of phrases and periods (for the local level) or sections or genre (for the global scale). Examples of common forms of Western music include the fugue, the invention, sonata-allegro, canon, strophic, theme and variations, and rondo. Popular Music often makes use of strophic form often in conjunction with Twelve bar blues.

Theories of harmonization
Four-part writing
Four part chorale writing is used to teach and analyze the basic conventions of Common-Practice Period music. In the German musicology tradition referred to as functional harmony. Johann Sebastian Bach's four voice chorales written for liturgical purposes serve as a model for students. These chorales exhibit a fusion of linear and vertical thinking. In analysis, the harmonic function and rhythm are analyzed as well as the shape and implications of each of the four lines. Students are then instructed to compose chorales, often using given melodies (as Bach would have done), over a given bass line, or to compose within a chord progression, following rules of voice leading. Though traditionally conceived as a vocal exercise for Soprano, Alto, Tenor, and Bass, other common four-part writings could consist of a brass quartet (two Trumpets, French Horn, and Trombone) or a string quartet (including violin I, violin II, viola and cello).
There are seven chords used in four-part writing that are based upon each note of the scale. The chords are usually given Roman Numerals I, II, III, IV, V, VI and VII to refer to triadic (three-note) chords which are based upon each successive note of the major or minor scale which the piece is in. Chords may be analyzed in two ways. Case-sensitive harmonic analysis would state that major-mode chords (I, IV, V7, etc.), including augmented (for example, VII+), would be notated with upper-case Roman numerals, and minor-mode chords, including diminished (ii, iii, vi, and the diminished vii chord, viio), would be notated with lower-case Roman numerals. Schenkerian harmonic analysis, patterned after the theories of Heinrich Schenker, would state that the mode does not matter in the final analysis, and thus all harmonies are notated in upper-case.
The skill in harmonising a Bach chorale lies in being able to begin a phrase in one key and to modulate to another key either at the end of the first phrase, the beginning of the next one, or perhaps by the end of the second phrase. Each chorale often has the ability to modulate to various tonally related areas: the relative major (III) or minor (vi), the Dominant (V) or its relative minor (iii), the Sub-Dominant (IV) or its relative minor (ii). Other chromatic chords may be used, like the diminished seventh (made up of minor thirds piled on top of each other) or the Secondary dominant (the Dominant's Dominant — a kind of major version of chord II). Certain standard cadences are observed, most notably IIb7 – V7 – I. The standard collection of J. S. Bach's chorales were edited by Albert Riemenschneider and this collection is readily available, e.g. here; the student is greatly rewarded by playing them at the piano, singing the lines by themselves, singing them in groups, analyzing them by writing the Key and the Chords employed and by taking the melody and bass line from any chorale and trying to fill in the inner alto and tenor parts. Once this has been accomplished the student can then begin to complete their own bass lines —whilst carefully watching for modulations— and then they can fill in the inner alto and tenor parts. Parallel octave and fifth motion is forbidden, and this often proves to be the pons asinorum of the average music student.

Music perception and cognition
Further information: Music cognition, Fred Lerdahl, and Ray Jackendoff
Jackendoff and Lerdahl attempt to develop a "musical grammar." Using Jackendoff's background as a linguist and Lerdahl's compositional and theoretical background, a series of generative rules are defined to explain the hierarchical structure of tonal music. The rules focus on musical grouping, or methods in which rhythmic groups of notes, as well as formal hierarchies, are perceived by listeners. Three sets of rules are given: "Grouping Well-Formedness Rules," "Grouping Preference Rules," and "Transformational Rules." These rules are designed to interpret how listeners group structures in tonal music. These groupings then play into the segmentation of events by listeners, which in turn determine the hierarchical structure perceived by the listener. Although this theory is well developed and complete, it is by far not the only system designed to discuss music in this manner, and there is no acceptance of this theory as being the sole theory by which to discuss perception of music (see Jonathan Kramer).

Serial composition and set theory
Further information: serialism, set theory (music), Arnold Schoenberg, Milton Babbitt, David Lewin, and Allen Forte
Twelve Tone Serialism is a technique developed by Arnold Schoenberg to order and repeat all the 12 pitches of the Chromatic Scale with specific order. An ordered row of the 12 pitches is created, then all possible transformations are explored. The analytic techniques involve writing a 12x12 matrix of the tone row, and all of its forms (Transposition, Inversion, Retrograde, Retrograde Inversion) This technique is strongly related to the composers of the Second Viennese School, but also has been incorporated into the languages of many other composers. Serialism does not always appear in the strict 12-note form; many composers have explored with serialism using fewer than 12 notes, repeating tones inside of the row, serialism of microtonal scales. Also, composers such as Pierre Boulez and his teacher Oliver Messiaen explored integral serialism, or the serialization of all possible musical parameters (pitch, rhythm, dynamics, etc.). Composers such as Igor Stravinsky and Milton Babbitt developed personal approaches to Serialism; Stravinsky using a method of Rotational Arrays, and Babbitt using Combinatoriality of the rows. Set Theory is another approach to understanding atonal music that may or may not be serial. Although more akin to the mathematical field of Group Theory than mathematical Set Theory, the nomenclature has become standard inside the musical community. Set theory represents the pitch classes as numbers to allow a methodology of examining music without tonic or triadic functional harmony. This technique allows for exploration of the construction of a serial tone row as well as less strict atonal works. This technique has been extended with a great deal of mathematical rigor to both tonal and atonal systems by David Lewin in his transformational approach utilizing networks of related sets.

Musical semiotics
Further information: music semiology and Jean-Jacques Nattiez

Notation
Main article: Musical notation
Musical notation is the symbolic representation of music (not to be confused with audio recording). Historically, and in the narrow sense, this is achieved with graphic symbols. Computer file formats have become important as well [1]. Spoken language and hand signs are also used to symbolically represent music, primarily in teaching.
In standard Western music notation, music is represented graphically by notes placed on a staff or staves with the vertical axis roughly corresponding to pitch and the horizontal axis roughly corresponding to time. Note head shapes, stems, flags, and ties are used to indicate duration. Additional symbols represent key, tempo, dynamics, accents, rests, etc.

Mathematics
Main article: Music and mathematics
Music and mathematics are strongly intertwined. As noted above, the concept of pitch and temperament are both strongly tied to mathematics, and acoustics in particular. Analysis often takes a mathematical route; musical set theory and Transformational theory are both steeped in mathematics.
Some methods of composition are mathematically based. Iannis Xenakis developed several methods using stochastic methods. The French school of spectral music uses mathematical analysis of sounds to develop compositional materials.

Analysis
Main articles: Musical analysis, Schenkerian analysis, and Transformational theory
Analysis is the effort to describe and explain music. Analysis at once is a catch-all term describing the process of describing any portion of the music, as well as a specific field of formal analysis or the field of stylistic analysis. Formal analysis attempts to answer questions of hierarchy and form, and stylistic analysis attempts to describe the style of the piece. These two distinct sub-fields often coincide.
Analysis of harmonic structures is typically presented through a roman numeral analysis. However, over the years, as music and the theory of music have both grown, a multitude of methods of analyzing music have presented themselves. Two very popular methods, Schenkerian analysis and Neo-Riemannian analysis, have dominated much of the field. Schenkerian analysis attempts to "reduce" music through layers of foreground, middleground, and, eventually and importantly, the background. Neo-Riemannian (or Transformational) analysis began as an extension of Hugo Riemann's theories of music, and then expanding Riemann's concepts of pitch and transformation into a mathematically rich language of analysis. While both theories originated as methods of analysis for tonal music, both have been extended to use in non-tonal music as well.

Ear training
Main article: Ear training
Aural skills — the ability to identify musical patterns by ear, as opposed to by the reading of notation — form a key part of a musician's craft and are usually taught alongside music theory. Most aural skills courses train the perception of relative pitch (the ability to determine pitch in an established context) and rhythm. Sight-singing — the ability to sing unfamiliar music without assistance — is generally an important component of aural skills courses.

see also:
http://en.wikipedia.org/wiki/Music_theory.