Editing Music theory (section)

===Scales and modes===
{{Main|Musical scale| Musical mode}}
[[File:C major scale.png|thumb|upright=1.3|A pattern of whole and half steps in the Ionian mode or major scale on C[[File:Ionian mode C.mid]]]]
Notes can be arranged in a variety of [[scale (music)|scale]]s and [[musical mode|modes]]. Western music theory generally divides the octave into a series of twelve pitches, called a [[chromatic scale]], within which the interval between adjacent tones is called a [[semitone]], or half step. Selecting tones from this set of 12 and arranging them in patterns of semitones and whole tones creates other scales.{{sfn|Touma|1996|loc={{Page needed|date=August 2014}}}}

The most commonly encountered scales are the seven-toned [[major scale|major]], the [[harmonic minor]], the [[melodic minor]], and the [[natural minor]]. Other examples of scales are the [[octatonic scale]] and the [[pentatonic]] or five-tone scale, which is common in [[folk music]] and [[blues]]. Non-Western cultures often use scales that do not correspond with an equally divided twelve-tone division of the octave. For example, classical [[Ottoman classical music|Ottoman]], [[Persian classical music|Persian]], [[Indian classical music|Indian]] and [[Arabic music|Arabic]] musical systems often make use of multiples of quarter tones (half the size of a semitone, as the name indicates), for instance in 'neutral' seconds (three quarter tones) or 'neutral' thirds (seven quarter tones)—they do not normally use the quarter tone itself as a direct interval.{{sfn|Touma|1996|loc={{Page needed|date=August 2014}}}}

In traditional Western notation, the scale used for a composition is usually indicated by a [[key signature]] at the beginning to designate the pitches that make up that scale. As the music progresses, the pitches used may change and introduce a different scale. Music can be [[Transposition (music)|transposed]] from one scale to another for various purposes, often to accommodate the range of a vocalist. Such transposition raises or lowers the overall pitch range, but preserves the intervallic relationships of the original scale. For example, transposition from the key of C major to D major raises all pitches of the scale of C major equally by a [[whole tone]]. Since the interval relationships remain unchanged, transposition may be unnoticed by a listener, however other qualities may change noticeably because transposition changes the relationship of the overall pitch [[range (music)|range]] compared to the range of the instruments or voices that perform the music. This often affects the music's overall sound, as well as having technical implications for the performers.{{sfn|Forsyth|1935|loc=73–74}}

The interrelationship of the keys most commonly used in Western tonal music is conveniently shown by the [[circle of fifths]]. Unique key signatures are also sometimes devised for a particular composition. During the Baroque period, emotional associations with specific keys, known as the [[doctrine of the affections]], were an important topic in music theory, but the unique tonal colorings of keys that gave rise to that doctrine were largely erased with the adoption of equal temperament. However, many musicians continue to feel that certain keys are more appropriate to certain emotions than others. [[Indian classical music]] theory continues to strongly associate keys with emotional states, times of day, and other extra-musical concepts and notably, does not employ equal temperament.