Synergistic tension among the music and lyrics of late-Romantic choral songs.

Songs combine two defining human capacities: music and language. As a song unfolds, interconnected musical and linguistic elements, such as dissonant chords and evocative words, generate fluctuating patterns of tension and relaxation that shape listeners' expectations and emotional experience. However, how these patterns integrate across the musical and linguistic domains to produce a unified sense of tension remains poorly understood. We investigated this question in a tension-rich subset of Western vocal music - late-Romantic choral songs - hypothesising that tonal and semantic tension combine superadditively. Using a naturalistic listening paradigm, online participants continuously rated tonal, semantic, and holistic tension while listening to three selected songs by Reger, Wolf, and Brahms. Holistic tension ratings were more closely predicted by tonal than by semantic tension. Information-theoretic analysis using Partial Information Decomposition further revealed significant redundant and synergistic informational contributions specifically in the Reger piece. This suggests that, under certain musical conditions - such as dense chromatic harmony combined with homophonic text setting - musical and linguistic cues can interact to produce integrated experiences of tension. Although based on a specific tonal-poetic idiom, these results further our understanding of how music and language may combine during real-time song listening from the experiential perspective of tension. We discuss how both culture-specific and potentially culture-invariant mechanisms may contribute to this cross-domain aesthetic integration.