Cross-cultural analysis of song
It is unclear whether there are universal patterns to music across cultures. Mehr et al. examined ethnographic data and observed music in every society sampled (see the Perspective by Fitch and Popescu). For songs specifically, three dimensions characterize more than 25% of the performances studied: formality of the performance, arousal level, and religiosity. There is more variation in musical behavior within societies than between societies, and societies show similar levels of within-society variation in musical behavior. At the same time, one-third of societies significantly differ from average for any given dimension, and half of all societies differ from average on at least one dimension, indicating variability across cultures.
Music is often assumed to be a human universal, emerging from an evolutionary adaptation specific to music and/or a by-product of adaptations for affect, language, motor control, and auditory perception. But universality has never actually been systematically demonstrated, and it is challenged by the vast diversity of music across cultures. Hypotheses of the evolutionary function of music are also untestable without comprehensive and representative data on its forms and behavioral contexts across societies.
We conducted a natural history of song: a systematic analysis of the features of vocal music found worldwide. It consists of a corpus of ethnographic text on musical behavior from a representative sample of mostly small-scale societies, and a discography of audio recordings of the music itself. We then applied tools of computational social science, which minimize the influence of sampling error and other biases, to answer six questions. Does music appear universally? What kinds of behavior are associated with song, and how do they vary among societies? Are the musical features of a song indicative of its behavioral context (e.g., infant care)? Do the melodic and rhythmic patterns of songs vary systematically, like those patterns found in language? And how prevalent is tonality across musical idioms?
Analysis of the ethnography corpus shows that music appears in every society observed; that variation in song events is well characterized by three dimensions (formality, arousal, religiosity); that musical behavior varies more within societies than across them on these dimensions; and that music is regularly associated with behavioral contexts such as infant care, healing, dance, and love. Analysis of the discography corpus shows that identifiable acoustic features of songs (accent, tempo, pitch range, etc.) predict their primary behavioral context (love, healing, etc.); that musical forms vary along two dimensions (melodic and rhythmic complexity); that melodic and rhythmic bigrams fall into power-law distributions; and that tonality is widespread, perhaps universal.
Music is in fact universal: It exists in every society (both with and without words), varies more within than between societies, regularly supports certain types of behavior, and has acoustic features that are systematically related to the goals and responses of singers and listeners. But music is not a fixed biological response with a single prototypical adaptive function: It is produced worldwide in diverse behavioral contexts that vary in formality, arousal, and religiosity. Music does appear to be tied to specific perceptual, cognitive, and affective faculties, including language (all societies put words to their songs), motor control (people in all societies dance), auditory analysis (all musical systems have signatures of tonality), and aesthetics (their melodies and rhythms are balanced between monotony and chaos). These analyses show how applying the tools of computational social science to rich bodies of humanistic data can reveal both universal features and patterns of variability in culture, addressing long-standing debates about each.
We used primary ethnographic text and field recordings of song performances to build two richly annotated cross-cultural datasets: NHS Ethnography and NHS Discography. The original material in each dataset was annotated by humans (both amateur and expert) and by automated algorithms.
What is universal about music, and what varies? We built a corpus of ethnographic text on musical behavior from a representative sample of the world’s societies, as well as a discography of audio recordings. The ethnographic corpus reveals that music (including songs with words) appears in every society observed; that music varies along three dimensions (formality, arousal, religiosity), more within societies than across them; and that music is associated with certain behavioral contexts such as infant care, healing, dance, and love. The discography—analyzed through machine summaries, amateur and expert listener ratings, and manual transcriptions—reveals that acoustic features of songs predict their primary behavioral context; that tonality is widespread, perhaps universal; that music varies in rhythmic and melodic complexity; and that elements of melodies and rhythms found worldwide follow power laws.
At least since Henry Wadsworth Longfellow declared in 1835 that “music is the universal language of mankind” (1), the conventional wisdom among many authors, scholars, and scientists is that music is a human universal, with profound similarities across societies (2). On this understanding, musicality is embedded in the biology of Homo sapiens (3), whether as one or more evolutionary adaptations for music (4, 5), the by-products of adaptations for auditory perception, motor control, language, and affect (6–9), or some amalgam of these.
Music certainly is widespread (10–12), ancient (13), and appealing to almost everyone (14). Yet claims that it is universal or has universal features are commonly made without citation [e.g., (15–17)], and those with the greatest expertise on the topic are skeptical. With a few exceptions (18), most music scholars suggest that few if any universals exist in music (19–23). They point to variability in the interpretations of a given piece of music (24–26), the importance of natural and social environments in shaping music (27–29), the diverse forms of music that can share similar behavioral functions (30), and the methodological difficulty of comparing the music of different societies (12, 31, 32). Given these criticisms, along with a history of some scholars using comparative work to advance erroneous claims of cultural or racial superiority (33), the common view among music scholars today (34, 35) is summarized by the ethnomusicologist George List: “The only universal aspect of music seems to be that most people make it. … I could provide pages of examples of the non-universality of music. This is hardly worth the trouble” (36).
Are there, in fact, meaningful universals in music? No one doubts that music varies across cultures, but diversity in behavior can shroud regularities emerging from common underlying psychological mechanisms. Beginning with Chomsky’s hypothesis that the world’s languages conform to an abstract Universal Grammar (37, 38), many anthropologists, psychologists, and cognitive scientists have shown that behavioral patterns once considered arbitrary cultural products may exhibit deeper, abstract similarities across societies emerging from universal features of human nature. These include religion (39–41), mate preferences (42), kinship systems (43), social relationships (44, 45), morality (46, 47), violence and warfare (48–50), and political and economic beliefs (51, 52).
Music may be another example, although it is perennially difficult to study. A recent analysis of the Garland Encyclopedia of World Music revealed that certain features—such as the use of words, chest voice, and an isochronous beat—appear in a majority of songs recorded within each of nine world regions (53). But the corpus was sampled opportunistically, which made generalizations to all of humanity impossible; the musical features were ambiguous, leading to poor interrater reliability; and the analysis studied only the forms of the societies’ music, not the behavioral contexts in which it is performed, leaving open key questions about functions of music and their connection to its forms.
Music perception experiments have begun to address some of these issues. In one, internet users reliably discriminated dance songs, healing songs, and lullabies sampled from 86 mostly small-scale societies (54); in another, listeners from the Mafa of Cameroon rated “happy,” “sad,” and “fearful” examples of Western music somewhat similarly to Canadian listeners, despite having had limited exposure to Western music (55); in a third, Americans and Kreung listeners from a rural Cambodian village were asked to create music that sounded “angry,” “happy,” “peaceful,” “sad,” or “scared” and generated similar melodies to one another within these categories (56). These studies suggest that the form of music is systematically related to its affective and behavioral effects in similar ways across cultures. But they can only provide provisional clues about which aspects of music, if any, are universal, because the societies, genres, contexts, and judges are highly limited, and because they too contain little information about music’s behavioral contexts across cultures.
A proper evaluation of claims of universality and variation requires a natural history of music: a systematic analysis of the features of musical behavior and musical forms across cultures, using scientific standards of objectivity, representativeness, quantification of variability, and controls for data integrity. We take up this challenge here. We focus on vocal music (hereafter, song) rather than instrumental music [see (57)] because it does not depend on technology, has well-defined physical correlates [i.e., pitched vocalizations (19)], and has been the primary focus of biological explanations for music (4, 5).
Leveraging more than a century of research from anthropology and ethnomusicology, we built two corpora, which collectively we call the Natural History of Song (NHS). The NHS Ethnography is a corpus of descriptions of song performances, including their context, lyrics, people present, and other details, systematically assembled from the ethnographic record to representatively sample diversity across societies. The NHS Discography is a corpus of field recordings of performances of four kinds of song—dance, healing, love, and lullaby—from an approximately representative sample of human societies, mostly small-scale.
We used the corpora to test five sets of hypotheses about universality and variability in musical behavior and musical forms:
1) We tested whether music is universal by examining the ethnographies of 315 societies, and then a geographically stratified pseudorandom sample of them.
2) We assessed how the behaviors associated with song differ among societies. We reduced the high-dimensional NHS Ethnography annotations to a small number of dimensions of variation while addressing challenges in the analysis of ethnographic data, such as selective nonreporting. This allowed us to assess how the variation in musical behavior across societies compares with the variation within a single society.
3) We tested which behaviors are universally or commonly associated with song. We cataloged 20 common but untested hypotheses about these associations, such as religious activity, dance, and infant care (4, 5, 40, 54, 58–60), and tested them after adjusting for sampling error and ethnographer bias, problems that have bedeviled prior tests.
4) We analyzed the musical features of songs themselves, as documented in the NHS Discography. We derived four representations of each song, including blind human ratings and machine summaries. We then applied machine classifiers to these representations to test whether the musical features of a song predict its association with particular behavioral contexts.
5) In exploratory analyses, we assessed the prevalence of tonality in the world’s songs, found that variation in their annotations falls along a small number of dimensions, and plotted the statistical distributions of melodic and rhythmic patterns in them.
All data and materials are publicly available at http://osf.io/jmv3q. We also encourage readers to view and listen to the corpora interactively via the plots available at http://themusiclab.org/nhsplots.
Music appears in all measured human societies
Is music universal? We first addressed this question by examining the eHRAF World Cultures database (61, 62), developed and maintained by the Human Relations Area Files organization. It includes high-quality ethnographic documents from 315 societies, subject-indexed by paragraph. We searched for text that was tagged as including music (instrumental or vocal) or that contained at least one keyword identifying vocal music (e.g., “singers”).
Music was widespread: The eHRAF ethnographies describe music in 309 of the 315 societies. Moreover, the remaining six (the Turkmen, Dominican, Hazara, Pamir, Tajik, and Ghorbat peoples) do in fact have music, according to primary ethnographic documents available outside the database (63–68). Thus, music is present in 100% of a large sample of societies, consistent with the claims of writers and scholars since Longfellow (1, 4, 5, 10, 12, 53, 54, 58–60, 69–73). Given these data, and assuming that the sample of human societies is representative, the Bayesian 95% posterior credible interval for the population proportion of human societies that have music, with a uniform prior, is [0.994, 1].
To examine what about music is universal and how music varies worldwide, we built the NHS Ethnography (Fig. 1 and Text S1.1), a corpus of 4709 descriptions of song performances drawn from the Probability Sample File (74–76). This is a ~45-million-word subset of the 315-society database, comprising 60 traditionally living societies that were drawn pseudorandomly from each of Murdock’s 60 cultural clusters (62), covering 30 distinct geographical regions and selected to be historically mostly independent of one another. Because the corpus representatively samples from the world’s societies, it has been used to test cross-cultural regularities in many domains (46, 77–83), and these regularities may be generalized (with appropriate caution) to all societies.
The illustration depicts the sequence from acts of singing to the ethnography corpus. (A) People produce songs in conjunction with other behavior, which scholars observe and describe in text. These ethnographies are published in books, reports, and journal articles and then compiled, translated, cataloged, and digitized by the Human Relations Area Files organization. (B) We conduct searches of the online eHRAF corpus for all descriptions of songs in the 60 societies of the Probability Sample File and annotate them with a variety of behavioral features. The raw text, annotations, and metadata together form the NHS Ethnography. Codebooks listing all available data are in tables S1 to S6; a listing of societies and locations from which texts were gathered is in table S12.
The NHS Ethnography, it turns out, includes examples of songs in all 60 societies. Moreover, each society has songs with words, as opposed to just humming or nonsense syllables (which are reported in 22 societies). Because the societies were sampled independently of whether their people were known to produce music, in contrast to prior cross-cultural studies (10, 53, 54), the presence of music in each one—as recognized by the anthropologists who embedded themselves in the society and wrote their authoritative ethnographies—constitutes the clearest evidence supporting the claim that song is a human universal. Readers interested in the nature of the ethnographers’ reports, which bear on what constitutes “music” in each society [see (27)], are encouraged to consult the interactive NHS Ethnography Explorer at http://themusiclab.org/nhsplots.