Editing Harmony (section)

== Perception ==
[[Image:Major triad.svg|upright=1.5|thumb|The harmonious [[Major chord|major triad]] is composed of three tones. Their frequency ratio corresponds approximately 6:5:4. In real performances, however, the third is often larger than 5:4. The ratio 5:4 corresponds to an interval of 386 [[Cent (music)|cents]], but an equally tempered major third is 400 cents and a Pythagorean third with a ratio of 81:64 is 408 cents. Measurements of frequencies in good performances confirm that the size of the major third varies across this range and can even lie outside it without sounding out of tune. Thus, there is no simple connection between frequency ratios and harmonic function.]]

A number of features contribute to the perception of a chord's harmony.

=== Tonal fusion ===
Tonal fusion contributes to the perceived consonance of a chord,<ref name=":0">{{Cite journal|last=Bidelman|first=Gavin M.|date=2013|title=The Role of the Auditory Brainstem in Processing Musically Relevant Pitch|journal=Frontiers in Psychology|volume=4|page=264|doi=10.3389/fpsyg.2013.00264|issn=1664-1078|pmc=3651994|pmid=23717294|doi-access=free}}</ref> describing the degree to which multiple pitches are heard as a single, unitary tone.<ref name=":0" /> Chords which have more coinciding partials (frequency components) are perceived as more consonant, such as the [[octave]] and [[perfect fifth]]. The spectra of these intervals resemble that of a uniform tone. According to this definition, a [[major triad]] fuses better than a [[minor triad]] and a [[Dominant seventh chord|major-minor seventh chord]] fuses better than a [[Major seventh chord|major-major seventh]] or [[Minor seventh chord|minor-minor seventh]]. These differences may not be readily apparent in tempered contexts but can explain why major triads are generally more prevalent than minor triads and major-minor sevenths are generally more prevalent than other sevenths (in spite of the dissonance of the tritone interval) in mainstream tonal music.

In organ registers, certain harmonic interval combinations and chords are activated by a single key. The sounds produced fuse into one tone with a new timbre. This tonal fusion effect is also used in synthesizers and orchestral arrangements; for instance, in [[Ravel]]'s Bolero #5 the parallel parts of flutes, horn and celesta resemble the sound of an electric organ.<ref name="Tanguiane1993">{{Cite book|last=Tanguiane (Tangian) |first=Andranick |date=1993|title= Artificial Perception and Music Recognition|series= Lecture Notes in Artificial Intelligence|volume=746|publisher=Springer |location=Berlin-Heidelberg|isbn=978-3-540-57394-4}}</ref><ref name="Tangian1994">{{Cite journal |last=Tanguiane (Tangian)|first=Andranick  |year=1994|title= A principle of correlativity of perception and its application to music recognition|journal=  Music Perception|volume=11 |issue=4 |pages=465–502|doi= 10.2307/40285634 |jstor=40285634 }}</ref>

=== Roughness ===
When adjacent harmonics in complex tones interfere with one another, they create the perception of what is known as "beating" or "roughness". These precepts are closely related to the perceived dissonance of chords.<ref>{{Cite journal|last1=Langner|first1=Gerald|last2=Ochse|first2=Michael|date=2006|title=The neural basis of pitch and harmony in the auditory system|url=http://dx.doi.org/10.1177/102986490601000109|journal=Musicae Scientiae|volume=10|issue=1_suppl|pages=185–208|doi=10.1177/102986490601000109|s2cid=144133151|issn=1029-8649|url-access=subscription}}</ref> To interfere, partials must lie within a critical bandwidth, which is a measure of the ear's ability to separate different frequencies.<ref>{{Cite journal|last1=Plomp|first1=R.|last2=Levelt|first2=W. J. M.|date=1965|title=Tonal Consonance and Critical Bandwidth|url=http://dx.doi.org/10.1121/1.1909741|journal=The Journal of the Acoustical Society of America|volume=38|issue=4|pages=548–560|doi=10.1121/1.1909741|pmid=5831012|bibcode=1965ASAJ...38..548P|issn=0001-4966|hdl=11858/00-001M-0000-0013-29B7-B|s2cid=15852125 |hdl-access=free}}</ref> Critical bandwidth lies between 2 and 3 semitones at high frequencies and becomes larger at lower frequencies.<ref>{{Cite journal|last1=Schellenberg|first1=E. Glenn|last2=Trehub|first2=Sandra E.|date=1994|title=Frequency ratios and the perception of tone patterns|journal=Psychonomic Bulletin & Review|volume=1|issue=2|pages=191–201|doi=10.3758/bf03200773|pmid=24203470|issn=1069-9384|doi-access=free}}</ref> The roughest interval in the [[chromatic scale]] is the [[Minor Second|minor second]] and its [[Inversion (music)|inversion]], the major seventh. For typical [[spectral envelope]]s in the central range, the second roughest interval is the major second and minor seventh, followed by the tritone, the minor third ([[major sixth]]), the major third ([[minor sixth]]) and the perfect fourth (fifth).<ref>{{Cite journal|last=Parncutt|first=Richard|date=1988|title=Revision of Terhardt's Psychoacoustical Model of the Root(s) of a Musical Chord|url=http://dx.doi.org/10.2307/40285416|journal=Music Perception|volume=6|issue=1|pages=65–93|doi=10.2307/40285416|jstor=40285416|issn=0730-7829|url-access=subscription}}</ref>

=== Familiarity ===
Familiarity also contributes to the perceived harmony of an interval. Chords that have often been heard in musical contexts tend to sound more consonant. This principle explains the gradual historical increase in harmonic complexity of Western music. For example, around 1600 unprepared seventh chords gradually became familiar and were therefore gradually perceived as more consonant.<ref>{{Cite journal|last=Parncutt|first=Richard|date=2011|title=The Tonic as Triad: Key Profiles as Pitch Salience Profiles of Tonic Triads|url=http://dx.doi.org/10.1525/mp.2011.28.4.333|journal=Music Perception|volume=28|issue=4|pages=333–366|doi=10.1525/mp.2011.28.4.333|issn=0730-7829|url-access=subscription}}</ref>

Individual characteristics such as age and musical experience also have an effect on harmony perception.<ref>{{Cite journal|last1=Bidelman|first1=Gavin M.|last2=Gandour|first2=Jackson T.|last3=Krishnan|first3=Ananthanarayan|date=2011|title=Musicians demonstrate experience-dependent brainstem enhancement of musical scale features within continuously gliding pitch|journal=Neuroscience Letters|volume=503|issue=3|pages=203–207|doi=10.1016/j.neulet.2011.08.036|pmid=21906656|issn=0304-3940|pmc=3196385}}</ref><ref name=":1">{{Cite journal|last1=Bones|first1=O.|last2=Plack|first2=C. J.|date=2015-03-04|title=Losing the Music: Aging Affects the Perception and Subcortical Neural Representation of Musical Harmony|journal=Journal of Neuroscience|volume=35|issue=9|pages=4071–4080|doi=10.1523/jneurosci.3214-14.2015|pmid=25740534|pmc=4348197|issn=0270-6474|doi-access=free}}</ref>

===Neural correlates of harmony===
The [[inferior colliculus]] is a mid-brain structure which is the first site of [[Binaural hearing|binaural auditory integration]], processing auditory information from the left and right ears.<ref>{{Cite journal|last1=Ito|first1=Tetsufumi|last2=Bishop|first2=Deborah C.|last3=Oliver|first3=Douglas L.|date=2015-10-26|title=Functional organization of the local circuit in the inferior colliculus|journal=Anatomical Science International|volume=91|issue=1|pages=22–34|doi=10.1007/s12565-015-0308-8|pmid=26497006|issn=1447-6959|pmc=4846595}}</ref> [[Frequency following response]]s (FFRs) recorded from the [[Midbrain|mid-brain]] exhibit peaks in activity which correspond to the frequency components of a tonal stimulus.<ref name=":1" /> The extent to which FFRs accurately represent the harmonic information of a chord is called neural salience, and this value is correlated with behavioral ratings of the perceived pleasantness of chords.<ref name=":1" />

In response to harmonic intervals, cortical activity also distinguishes chords by their consonance, responding more robustly to chords with greater consonance.<ref name=":0" />