Music Theory

Melody

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.

Pitch

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

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

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 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.