Overtone Singing as Natural Theta–Gamma Cross-Frequency Neuromodulation

Overtone singing is a vocal technique in which a single performer simultaneously produces a sustained fundamental frequency and one or more clearly audible reinforced harmonics by precise manipulation of the vocal tract resonances. Recent magnetoencephalographic (MEG) evidence demonstrates that overtone-rich auditory stimuli drive a pronounced increase in cortical theta-band power (4–8 Hz) with right-hemispheric lateralization, with stimulus type explaining a large proportion of the variance in hemispheric activation patterns in listeners (Saus, Seither-Preisler, & Schneider, 2025). Independently, a substantial body of neuroscience research has established that theta-gamma cross-frequency coupling (TGC), the phase-amplitude modulation of gamma oscillations (~30–80 Hz) by theta rhythms, is a core mechanism supporting working memory, and that its degradation is among the earliest neurophysiological markers of Alzheimer's disease and mild cognitive impairment (Goodman et al., 2018; Goutagny et al., 2013).

Here, I propose that active performance of overtone singing generates a unique neurophysiological state in which theta-dominant auditory self-stimulation co-occurs with gamma-band activation from fine motor control, focused attention, and auditory–motor feedback integration. This simultaneous dual-band engagement may create conditions that enhance theta-gamma coupling endogenously, constituting a form of natural, non-technological cross-frequency neuromodulation analogous to what transcranial alternating current stimulation (tACS) achieves artificially (Kolhoff et al., 2024). The Cytoelectric Coupling Hypothesis (Pinotsis, Fridman, & Miller, 2023), which demonstrates that endogenous electric fields organize neural ensembles from macroscale to cytoskeletal levels with particular efficacy at slow (<8 Hz) frequencies, provides a biophysical mechanism by which strong theta oscillations could serve as a field-level scaffold for organizing gamma-band activity. If confirmed, overtone singing practice could represent an accessible, non-pharmacological intervention with potential neuroprotective benefits for cognitive aging and neurodegenerative conditions.