Spectral traits of multiphonic vocalizations in extreme metal genres

Extreme metal vocal techniques include specialized growls and screams of death metal and black metal, as well as emotive roars of neighboring genres like deathcore. We analyze differences between harmonic and inharmonic signals produced in these vocal styles. Harmonic styles are an example of a true multi-phonic vocalization, with fundamental-frequency components resulting from the oscillation of the true vocal folds combined with concurrent inharmonic elements provided by additional vibrating tissues. These styles resulted in and gradual spectral shifts across the duration of the phonation. Conversely, inharmonic styles lack fundamentals and display rapid spectral fluctuations with greater amplitude variability. We employed multimodal imaging techniques, specifically nasoendoscopy and dynamic magnetic resonance imaging (MRI), to visualize physiological mechanisms during vocal production. These imaging data were synchronized with audio recordings to analyze amplitude modulation, spectral characteristics, and temporal evolution. Laryngeal electromyography provided insight into intrinsic laryngeal muscle activation, and aerodynamic data were also captured to measure airflow, pressure, and volume. Time-frequency analyses show harmonic vocalizations follow predictable spectral trajectories, while inharmonic styles exhibit abrupt variations. These findings suggest acoustical traits carry implications about intimidating size and ferocity, advancing understanding of physiological substrates underlying extreme metal vocalizations.