What is Music? The Super-Stimulus Theory Philip Dorrell philip (funny email character) 1729 (little dot) com 14 Chetwode Grove, Newlands, Wellington, New Zealand. What is Music? – p. 1/84
Introduction What is Music? – p. 2/84
Who is Philip Dorrell? Mostly work as a software developer. Not a professional scientist, mathematician or anything else relevant to music science. Enthusiastic amateur. Interests include: Mathematics Science Reckless and imprudent application of previous two items to other fields of endeavour: Human society, morality, politics The human mind: consciousness, dreams Music http://www.1729.com/ What is Music? – p. 3/84
My Book “What is Music? Solving a Scientific Mystery” Self-published Web site: http://whatismusic.info/ Currently available via POD at lulu.com for US$30 + postage What is Music? – p. 4/84
What is Music? (Part 1) Music is a subjective phenomenon. We experience: Pleasure Emotion We observe that others respond to music. We can describe features of music that we observe: Melody: scales Harmony: chords, bass, home chords Rhythm: bars, metre, note lengths But, the description is incomplete . What is Music? – p. 5/84
What is Music? (Part 2) A complete theory should ... explain what happens inside our brains when we listen to music, relate this to evolution by natural selection: What is the purpose of music? give us a complete description of music, correspond to our subjective experience of music. What is Music? – p. 6/84
The Luxury Yacht Test 1. Discover complete theory of music. 2. From theory, determine a generative algorithm for music. 3. Use algorithm to generate new original strong music. 4. Profit! 5. Purchase luxury yacht. What is Music? – p. 7/84
Existing Music Science: Assumptions Evolutionary Assumption: Good, but many implausible hypotheses Music Assumption: Music has a purpose. Communication Hypothesis: Music is communication. Social Assumption: Music has a social purpose. “In the Past” Assumption: Music used to serve a purpose. Music-Language Assumption: Yes, but how? Musical “syntax” theories. Cultural Assumption: It’s all culturally defined. What is Music? – p. 8/84
Neuroscientific Assumptions Cortical Plasticity Assumption: The brain adapts to general features of music (not pre-adapted). Temporal Coding: timings of neural firing in phase with sound vibrations What is Music? – p. 9/84
Musical Aspect Assumptions Simultaneous Pitch Assumption: Brain mechanisms for detecting relationships between simultaneous pitch values. (But why should it care?) Scale Assumption: Plasticity, Categorisation Hierarchical Segmentation: time bars beats shortest beat period What is Music? – p. 10/84
Music & Musicality What is Music? – p. 11/84
Purpose of Music Which aspect of music has the purpose? Composing music? Performing music? Listening to (and responding to) music? Are we assuming too much? The Music Assumption: Music itself has a purpose. Alternative: Music is a side-effect (of something else). What is Music? – p. 12/84
Information Processing The brain is an information processing system . Music is information . But what does it mean ? What is Music? – p. 13/84
Music = input or output? Hypothesis: Music is primarily an input. Almost everyone appreciates good music. Creating music good enough to listen to is non-trivial: Performance requires skill and practice. Composition is very difficult. What is Music? – p. 14/84
input = Music, output = ? What is Music? – p. 15/84
input = Music, output = Musicality Hypothesis: The output is “musicality”: how good the music is. But what is the meaning of musicality? Apparently 1-dimensional What is Music? – p. 16/84
Does music have a purpose? The goal of composition and performance is to create good music. Music exists because it is musical. Musicality is a perceived property of music. Too circular: no plausible selective pressure. What is Music? – p. 17/84
Perception of Musicality Hypothesis: Musicality is a property of something else. What? What other thing is like music? Answer: Speech. Common features of speech and music: “Melody” “Rhythm” Vocal Timbre What is Music? – p. 18/84
The Musicality of Speech Hypothesis: Musicality is a perceived aspect of speech. Music is (obviously) much more musical than speech. Music is a super-stimulus . What is Music? – p. 19/84
What does Musicality Mean? If musicality is a perceived aspect of speech – What does it mean? For the moment, leave this unanswered. Proceed on assumption that it is some property that matters. What is Music? – p. 20/84
Compare Matching Aspects Melody: Speech: (mostly) continuous Music: discontinuous, notes come from scales (but often as close to continuous as is permitted by scale constraint) Rhythm: Speech: irregular Music: regular and hierarchical Timbre (exact match): The human voice is a preferred musical instrument. Other instruments make voice-like sounds. What is Music? – p. 21/84
Compare Non-Matching Aspects (part 1) For speech aspects not in music, assume they are not relevant to the determination of musicality. Phonemes Grammar Vocabulary Semantics These features do occur in song lyrics, but mostly satisfy consistency requirements : Words match rhythm of music. Words match melody (in tone languages). Semantics match emotion of music. What is Music? – p. 22/84
Compare Non-Matching Aspects (part 2) Certain aspects of music appear to have no equivalent in speech: Harmony Bass Scales Home notes and home chords Repetition What is Music? – p. 23/84
Super-stimulus Aspects Each speech aspect has a cortical map perceiving it. Each cortical map has a super-stimulus. Each such super-stimulus corresponds to an aspect of music. The super-stimulus may have properties not in the normal stimulus. This explanation applies to both matching and (apparently) non-matching aspects. What is Music? – p. 24/84
Individual Aspects What is Music? – p. 25/84
Harmony and Bass What is Music? – p. 26/84
Harmony (part 1) A “harmonic” cortical map responds to simultaneous pitch values, related by consonant intervals. No simultaneous pitch values in speech. But, harmonic map also responds to sequential pitch values, related by consonant intervals: Sequential and simultaneous playing of notes in a chord both give us the “feel” of the chord. Conclusion: The purpose of the harmonic cortical is to respond to consonant relationships between pitch values occurring at different times within one speech melody. What is Music? – p. 27/84
Bass A cortical map with greater response to low pitch values. The super-stimulus consists of very low pitch values. What is Music? – p. 28/84
Harmony (part 2) Observed properties of chords: Chords persist for one or more bars. A chord is a perceived property of that portion of the tune. Chords change on the main beat. Notes of a chord tend to be consonantly related to each other. Bass note = root note of chord. Chords are perceived modulo octaves. What is Music? – p. 29/84
Harmony (part 3) We can deduce the properties of the cortical map that responds to chords: Neurons have persistent response to pitch values that occur. Neural activity tends to be reset on a strong beat. Mutual reinforcement of activity between neurons representing pitch values separated by consonant intervals. Reinforcement of neural activity by activity in corresponding bass cortical map neurons. Neurons respond to pitch values modulo octaves (i.e. “chroma”). What is Music? – p. 30/84
Harmonic Map Response 5/2f 2f 3/2f 5/4f f 0 t0 t1 t2 t3 t4 t5 t6 What is Music? – p. 31/84
Rhythm What is Music? – p. 32/84
Rhythm (part 1) Response to regular beats Cortical map with 1 dimension = beat period. Multiple peaks in spectrum, for example for 4/4 time: 1 bar 1/2 bar = 2 notes 1/4 bar = 1 note 1/2 note 1/4 note What is Music? – p. 33/84
Regular Beat Cortical Map Response 4/4 time: 4/4 2000ms 1000ms 500ms 250ms 125ms Position in cortical map Irregular speech rhythm: Position in cortical map What is Music? – p. 34/84
Regular Beat Cortical Map: 6/8 time 6/8 1800ms 900ms 300ms 150ms Position in cortical map 6/8 960ms 480ms 160ms 80ms Position in cortical map What is Music? – p. 35/84
Rhythm (part 2) Note length Like regular beat, but without requirement for repetition Possible 2nd dimension to cortical map: one extreme = note length second extreme = regular beat in-between points could account for some syncopation effects What is Music? – p. 36/84
Scales What is Music? – p. 37/84
The Scale As a property of a tune Which pitch values have occurred recently? Persistent response Response to pitch value modulo octaves What is Music? – p. 38/84
Scale Map Response: Speech Pitch Time Intensity What is Music? – p. 39/84
Scale Map Response: Music Pitch Time Intensity What is Music? – p. 40/84
Scale Map Response: Music (Saturated) Pitch Time Intensity What is Music? – p. 41/84
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