T he normalized pairwise variability index (nPVI) is a measure originally used to compare the rhythms of languages. Patel and Daniele (2003a) introduced the nPVI to music research and it has since been used in a number of studies. In this paper, I present a methodological criticism of the nPVI as applied to music. I discuss the known qualitative features of the nPVI and illustrate the nPVI's fundamental features and assumptions through its application to a number of musical datasets. My principle criticism regards the application of a linear average (the nPVI) to categorical data (rhythmic notation). I argue that that simpler mathematical characterizations, which are more musically intuitive, can capture the same useful information as the nPVI. Specifically, counting the proportion of successive IOIs that are identical accounts for as much as 98% of variation in nPVIs in musical corpora. I argue that abstract mathematical measures ought to be avoided in preference for more concrete empirical descriptions of specific rhythmic features, and that, rather than focusing on a single measure, multiple measures ought to be used. Finally, I conclude that the usage of nPVI in music research should be limited to specific methodologically justified contexts.
Although purely instrumental music is commonplace, much of the world’s most popular music is sung with lyrics. However, it is evident that listeners don’t always attend to lyrics and that those who do aren’t always successful in deciphering them. An empirical study is reported whose goal is to measure the intelligibility of lyrics in commercial recordings of music from a variety of genres. Thirty participants were exposed to 120 brief musical excerpts from twelve song genres: Avante-garde, Blues, Classical, Country, Folk, Jazz, Musical Theater, Pop/Rock, Rhythm and Blues, Rap, Reggae, and Religious. Participants were instructed to transcribe the lyrics after hearing each excerpt once. The transcribed lyrics were then compared to the actual lyrics and intelligibility scores calculated. The different genres were found to exhibit significantly different levels of lyric intelligibility, from as low as 48% for Classical music, to as high as 96% for Jazz, with an overall average of 72%. Intelligibility scores were positively correlated with listener judgments of the general importance of lyrics. In a second experiment, participants were allowed to hear excerpts five times. Improvements to intelligibility were modest but significant after the second and third hearings, but not on further hearings.