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Music theory is a field of study that investigates the nature or mechanics of music. It often involves identifying patterns that govern composers' techniques. In a more general sense, music theory also often distills and analyzes the elements of music – rhythm, harmony, melody, structure, and texture.
A Melody is a series of pitches sounding in succession. In Western music, the notes of a melody are typically created with respect to scales or modes. The rhythm of a melody is often based on the inflections of language or the physical rhythms of dance. It is typically divided into phrases within a larger overarching structure.
Musical sounds are composed of pitch, duration, and timbre. Pitch is determined by the sound's frequency of vibration, such as the note A which at modern concert pitch is defined to be 440 Hz. Tuning is the process of assigning pitches to notes. The difference in pitch between two notes is called an interval. The most basic interval is the octave; a note and another note with twice its frequency form an octave, and if the pitch with frequency 440 Hz is A, then the pitches with frequency 880 Hz, 1760 Hz as well as 220 Hz, 110 Hz, and 55 Hz are also A's. Notes can be arranged into different scales and modes. In western music theory, the octave is divided into 12 notes, each called a half-step or semitone. Patterns of half and whole steps (2 half steps, or a tone) make up a scale in that octave. The scales most commonly encountered are the major, the harmonic minor, the melodic minor, and the natural minor.
In music written using the system of major-minor tonality, the key of a piece determines the scale used. Transposing a piece from C major to D major will make all the notes two semitones 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, changing the key in which a piece is performed may go unrecognized by the listener, since changing the key does not change the relationship of the individual pitches to each other. Therefore, different keys are often considered equivalent and a matter of choice on the part of performers. This is especially true for popular and folk songs.
Rhythm is the arrangement of sounds 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 Fred Lerdahl and Ray Jackendoff, Jonathan Kramer, Christopher Hasty, William Rothstein, and Joel Lester.
Harmony occurs when two or more pitches are sounded simultaneously, although harmony can be implied when pitches are sounded successively rather than simultaneously (as in arpeggiation). Two simultaneous pitches form a diad. Three or more different kinds of pitches sounded simultaneously are called chords, though the term is often used to indicate a particular organization of pitches, such as the triad, rather than just any three or more pitches.
Consonance and Dissonance
Consonance can be roughly defined as harmonies whose tones complement and augment 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.
Brief audio (MIDI) musical examples of the interaction and effect of consonance and dissonance upon each other can be found here: "The effect of context on dissonance" and here: "The role of harmony in music"
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 judgment, in contrast with a more common usage of "in harmony" or "harmonious", which in technical language might be described as consonance.
An exercise often set to develop and test a student's grasp of the workings of harmonic conventions is the writing of four-part harmony. This exercise is often given bass line or a given melody. Four-part writing can be used to write for a vocal quartet, or an instrumental quartet. Vocal four-part harmonies usually consist of a soprano, an alto, a tenor, and a bass. The soprano and alto are usually female parts and the tenor and bass are most often male, although some female vocalists may sing tenor and male singers may carry the alto voice. Other common four-part writings consist of a brass quartet with a trumpet, a french horn, a trombone, and a tuba, or a string quartet consiting of two violin parts, a viola part, and a cello part.
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.
Musical structure refers to the overarching form of a piece of music. Examples of popular Western structures include the fugue, the invention, sonata allegro, canon, song form, theme and variations, and rondo.
The form of a piece of music can be reduced to sections, and those sections can be reduced to musical phrases. Typically, a pause or strong sense of resolution indicates the end of a section, whereas smaller pauses and lesser sense of resolution indicate the ends of phrases within a section.
Music notation is the graphical representation of music. In standard Western notation, pitches are represented on the vertical axis and time is represented by notation symbols on the horizontal axis. Thus, notes are properly placed on the musical staff with appropriate time values to show musicians what note to play and when to play it.
Such notation makes up the contents of the musical staff, along with directions indicating the key, tempo, dynamics, accents, and rests, etc...
Music and mathematics
Music has been susceptible to analysis by mathematics, ever since Pythagoras noticed the relationships between the frequencies of different pitches.
Analysis attempts to answer the question "how does this music work".
Music perception and cognition
- Further information: Fred Lerdahl and Ray Jackendoff
12-tone and set theory
- Further information: serialism , set theory (music), Arnold Schoenberg, Milton Babbitt, David Lewin, and Allen Forte
- Further information: music semiology and Jean-Jacques Nattiez
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.
- Boretz, Benjamin (1995) Meta-Variations: Studies in the Foundations of Musical Thought. Red Hook, New York: Open Space.
- Taylor, Eric. AB Guide to Music. Vol 1. England. Associated Board of the Royal Schools of Music, 1989. ISBN 1-85472-446-0
- Taylor, Eric. AB Guide to Music. Vol 2. England. Associated Board of the Royal Schools of Music, 1991. ISBN 1-85472-447-9
- Music Theory & History Online
- Music Theory Online
- Music theory lesson for the guitar
- Computing in Musicology
- Ricci Adams' Free Online Music Theory Lessons.
- Journal of the Royal Musical Association
- NewMusicBox.org Theory Issue 48 - Vol.4, No.12, featuring an interview with Edward Cone
- Tonalsoft: Encyclopedia of Microtonal Music Theory
- teoría - a music theory web
- Natural Bases of Scales and The 7-Note Solution -- Why so many 5 & 7-note scales are found in ancient writings and artifacts.
- Glossary of US and British English musical terms
- Music Theory Newsgroup On Google Groups - rec.music.theory Usenet Newsgroup
- Application of virtual pitch theory in music analysis (PDF)
- Contemporary Impressionalistic Music Theory and Composition
- GOSK.com Simple explanation of the seven musical modes for guitarists