Consonant Chords Research Articles

Adaptive Computation for Sensing Acoustical Environmental Change in the Auditory Cortex

Mismatch Negativity (MMN) is an evoked potential in response to an acoustical environmental change. Hypothesizing that, for animals to survive, MMN plays important roles in sensing environmental atmosphere, we investigated MMN in the auditory cortex of anesthetized rats in response to changes of frequency and harmony of test tone pulses. We first confirmed in behavioral experiments that rats could categorize consonant and dissonant chords, and thus distinguish this kind of sound feature quality, or ‘qualia.’ In physiological experiments, a surface microelectrode array mapped auditory evoked middle-latency response (P1) and MMN. We found that MMN could be elicited from the difference of qualia between consonant and dissonant chords and that the distributions of chord-elicited MMN were different from those of tone-elicited MMN. In response to pure tones, while middle-latency response (P1) was focally evoked from primary and anterior auditory cortex (A1, AAF), MMN spread toward ventral auditory cortex (VAF) in addition to A1 and AAF. In response to chords, MMN also widely spread over the auditory cortex, yet the largest activation spot was obtained in AAF. We also found an asymmetric property of MMN: Changes from low- to high-frequency tones and from dissonant to consonant chords produced larger MMN. Taken together, MMN in the auditory cortex can be elicited by changes of distinguishable qualia in an asymmetric form, suggesting that MMN reflects a detection of change of particular environmental atmosphere of sounds, which are potentially important for a survival.

Consonant chords stimulate higher EEG gamma activity than dissonant chords

We examined the perceptions of consonant and dissonant chords to test auditory coherent percepts that are related to gamma oscillation. Consonant chords have coherent auditory properties due to the physical relationships of their components, in contrast to dissonant chords. EEGs were measured on 18 subjects with no musical expertise while they listened to consonant chords, dissonant chords, and single-note sounds and counted the number of single tones they heard. Induced gamma band activity was observed over the right brain hemisphere 170ms after the onset of stimuli. The induced gamma activity was significantly increased while listening to consonant chords as compared to dissonant chords. Our results suggest that the neural activity of the gamma frequency bands may reflect an auditory coherent percept generated from physical relationships of sounds.

Neural correlates of sensory consonance and dissonance in primate primary auditory cortex.

The perception of consonance and dissonance of isolated chords (sensory consonance/dissonance) is fundamental to music appreciation. Consonant chords are composed of tones related to each other by simple frequency ratios (e.g., perfect fifth 3:2), whereas dissonant chords are composed of tones related to each other by complex ratios (e.g., minor second 256:243). Dissonance is thought to be due to the perception of beats (modulation frequencies < 20 Hz) or roughness (modulation frequencies from 20–250 Hz), which occur when two or more components of a complex sound are separated from one another in frequency by less than the width of an auditory filter (i.e., critical bandwidth). These unresolved frequency components interact in the auditory periphery to produce amplitude-modulated (AM) fluctuations in the composite waveform envelope. We demonstrate that the magnitude of neuronal phase-locking to these AM fluctuations in primary auditory cortex of awake monkeys correlates with the perceived consonance/dissonance of musical chords and parallels human perception of roughness. This correlation is displayed by population activity, as measured by auditory evoked potentials (AEPs), current source density, and multiunit activity. We further demonstrate that phase-locking of AEPs in Heschl’s gyrus of humans is similar to that seen in the monkey.

The Birth of Musical Emotion

Intracranial electroencephalography was recorded in an epileptic patient when he was listening to dissonant and consonant chords and to minor and major chords. Changes in dissonance induced event-related potentials (ERPs) in the auditory areas from 200 ms onward, in the orbito-frontal cortex (500-1000 ms), and later in the amygdala and anterior cingulate gyrus (1200-1400 ms), suggesting the sequential involvement of these brain structures in implicit emotional judgment of musical dissonance. Changes in musical mode induced ERPs only in the orbito-frontal cortex (500-1000 ms), emphasizing the implication of this frontal region in emotional judgment of pleasant music.

Functional MRI/Event-related potential study of sensory consonance and dissonance in musicians and nonmusicians

Pleasurability of individual chords, known as sensory consonance, is widely regarded as physiologically determined and has been shown to be associated with differential activity in the auditory cortex and in several other regions. Here, we present results obtained contrasting isolated four-note chords classified as consonant or dissonant in tonal music. Using event-related functional MRI, consonant chords were found to elicit a larger haemodynamic response in the inferior and middle frontal gyri, premotor cortex and inferior parietal lobule. The effect was right lateralized for nonmusicians and less asymmetric for musicians. Using event-related potentials, the degree of sensory consonance was found to modulate the amplitude of the P1 in both groups and of the N2 in musicians only.

Discrete cortical regions associated with the musical beauty of major and minor chords

Previous research has demonstrated that the degree of aesthetic pleasure a person experiences correlates with the activation of reward functions in the brain. However, it is unclear whether different affective qualities and the perceptions of beauty that they evoke correspond to specific areas of brain activation. Major and minor musical keys induce two types of affective qualities--bright/happy and dark/sad--that both evoke aesthetic pleasure. In the present study, we used positron emission tomography to demonstrate that the two musical keys (major and minor) activate distinct brain areas. Minor consonant chords perceived as beautiful strongly activated the right striatum, which has been assumed to play an important role in reward and emotion processing, whereas major consonant chords perceived as beautiful induced significant activity in the left middle temporal gyrus, which is believed to be related to coherent and orderly information processing. These results suggest that major and minor keys, both of which are perceived as beautiful, are processed differently in the brain.

“Consonance” in Tonal Jazz: A Critical Survey of Its Semantic History

This paper considers the venerable history of efforts to define the terms “consonance” and “dissonance,” and highlights their most relevant meanings for the study of tonal jazz. While one can acknowledge a plurality of semantic diversity, none of the existing definitions taken individually can fully account for how the terms are used in most jazz parlance. Further, normative uses of the term “consonance” in the discipline of music theory can neither account for the stable harmonic sonorities that consist of chords with four or more members, nor account for the variety of chord options that can each fulfill the role of a stable sonority in the musical language of tonal jazz. To resolve the terminological problems, this approach defines consonance and dissonance as stable/passive and unstable/active harmonic entities within the musical grammar of tonal jazz, as influenced by sonorous euphony. This understanding of the terms thus embraces a pluralism of meaning that can account for the specific challenges in jazz such as its improvisational context, stylistic variety, and others. This plurality encompasses resolutions of conceptual dichotomies that have existed in different meanings of the terms since their first uses in ancient Greek sources. The article argues that because of the nature of the music, the definition of “consonance” in particular must be conceived in a relative, harmonic sense. In this approach, the article proffers three categories—or dialects—of consonant chords, based upon a sampling of jazz piano performances and pedagogical sources in jazz theory. In tonal jazz, all consonant chords include a major or minor triad in addition to one of three different possibilities of a fourth chord member: added sixth, minor seventh, or major seventh. Beyond these harmonic dialects of four‐note chords, other possibilities exist for extensions of the ninth and (sharp) eleventh. While these categories have been acknowledged by several pedagogical sources, this literature provides little or no context of harmonic function nor a systematic framework to model how the contextually stable chords behave. The idea that consonance can include chords beyond a triad is contrasted with existing literature in tonal theory, particularly extended Schenkerian theory that has been applied to jazz. While some of this literature acknowledges the stable roles played by the three primary dialect tones, almost all of them do not grant them equal status as the triadic tones in consonant harmonies. The article concludes by supporting the conclusions raised in the survey of jazz pedagogy and Schenkerian theory in a discussion of metaphoric musical meaning of tension and release.

Musical Chords as Affective Priming Context in a Word-Evaluation Task

Using an affective priming paradigm, we demonstrated that the affective tone of musical chords influences the evaluation of target words. In Experiment 1, participants heard either consonant chords with three tones or dissonant chords with four tones as primes and then saw a positive or a negative word as target. Even participants who were unaware of the hypothesis of the experiment evaluated target words faster if the words were preceded by a similarly valenced chord (e.g., consonant-holiday) as compared to affectively incongruent chord-word pairs (e.g. dissonanthumor). In Experiment 2, results of Experiment 1 were replicated even when chord density was held constant at three tones per chord. Results suggest that the affective tone of single musical elements is automatically extracted and might therefore be viewed as a basic process contributing to the strong connection between music and affect.

Effects of estrogen augmentation on cognition and symptoms in female schizophrenia patients

When musical notes are combined to make a chord, the closeness of fit of the combined spectrum to a single harmonic series (the ‘harmonicity’ of the chord) predicts the perceived consonance (how pleasant and stable the chord sounds; McDermott, Lehr, & Oxenham, 2010). The distinction between consonance and dissonance is central to Western musical form. Harmonicity is represented in the temporal firing patterns of populations of brainstem neurons. The current study investigates the role of brainstem temporal coding of harmonicity in the perception of consonance. Individual preference for consonant over dissonant chords was measured using a rating scale for pairs of simultaneous notes. In order to investigate the effects of cochlear interactions, notes were presented in two ways: both notes to both ears or each note to different ears. The electrophysiological frequency following response (FFR), reflecting sustained neural activity in the brainstem synchronised to the stimulus, was also measured. When both notes were presented to both ears the perceptual distinction between consonant and dissonant chords was stronger than when the notes were presented to different ears. In the condition in which both notes were presented to the both ears additional low-frequency components, corresponding to difference tones resulting from nonlinear cochlear processing, were observable in the FFR effectively enhancing the neural harmonicity of consonant chords but not dissonant chords. Suppressing the cochlear envelope component of the FFR also suppressed the additional frequency components. This suggests that, in the case of consonant chords, difference tones generated by interactions between notes in the cochlea enhance the perception of consonance. Furthermore, individuals with a greater distinction between consonant and dissonant chords in the FFR to individual harmonics had a stronger preference for consonant over dissonant chords. Overall, the results provide compelling evidence for the role of neural temporal coding in the perception of consonance, and suggest that the representation of harmonicity in phase locked neural firing drives the perception of consonance.

Keyboards for pure music

Let S45 be the set all rational numbers of the form m/n, where m and n are positive integers with mn?45. We define an instrument M with three keyboards I, II, and III. Keyboards I and II permit one to play all consonant chords for which there exists a value φ such that the ratio of φ to the frequency of each simple tone of the chord belongs to S45. Keyboard II is organized so that pressing the keys on some straight lines yields the consonant chords. Keyboard III controls the quality of tones. The purpose of M is not to perform the music of today, but, hopefully, to inspire a new kind of music.