Chants across seven traditions share acoustic traits that enhance subjective relaxation

For over 5,000 y, chanting has been practiced across many Western and Eastern traditions. However, there is hardly any empirical research on 1) whether chants from across the globe share common acoustic properties, 2) whether these acoustic features make them distinct from other human vocalizations, and 3) the extent to which they may positively impact listeners' well-being. Here, we collected 242 chants belonging to seven distinct traditions and associated with a wide range of language families, and compared them acoustically to a large corpus of song (n = 126) and speech (n = 616) samples from across 14 linguistic and 12 geographical regions. We show that, irrespective of language and geographical origin, chants share distinctive acoustic traits, namely relatively flat and slow-changing intonation and steady, unbroken voicing in a comfortable, rather low pitch range with a prevalence of mid-central vowels. Thus, chants are produced in a relaxed vocal tract configuration with minimal articulation. Additionally, playback experiments involving original chants (with a participant pool of 61 listeners), resynthesized chants (with 114 listeners), and fully synthetic chants (with 80 listeners) demonstrate that these acoustic characteristics enhance listeners' perceived sensations of relaxation. Specifically, relatively flat and slow-changing intonation, combined with vowel production in a relatively relaxed vocal tract configuration, resulted in higher overall relaxation ratings. Together these results hint at a specific function of chants' acoustic commonalities: the enhancement of well-being through relaxation.