Abstract
Background
The preterm infant leaves the womb still building its auditory brain, trading maternal voice and heartbeat for the noise of intensive care. Singing tries to hand some of that back, and is built almost entirely around the mother, without having ever tested this premise against the father or any other caregiver.Methods
In a registered trial (NCT06398912) we recorded EEG in preterm infants, each hearing the same stimuli-block from four facilitators (mother, father, female, and male music therapist) crossing kinship with F0/pitch. Delta-band power was the pre-registered primary outcome; the hypothesis was maternal dominance.Results
Hypothesis was not supported. The mother's apparent lead vanished once each session was referenced to its own baseline (silence), while results ran the other way: during the lullaby, the most complex stimulus, and the one the fixed order placed last against waning engagement, the father's voice drew the highest Delta power, and the two male voices together outdrew the female. Results held under bootstrap.Conclusion
The preterm cortex followed the male (father's foremost) low, spectrally full voice, providing a robust signal, pointing somewhere concrete: fathers, among the most sidelined figures in the NICU, may hold a defined, testable role in their own infant's care.Impact
The trial's registered prediction-that the maternal voice would most strongly engage the preterm brain-was not supported; during a sung lullaby, male voices, the father's foremost, evoked the largest short-term response. To our knowledge, this is the first full cohort qEEG evidence that a singer's biological sex, rather than maternal kinship, tracks the preterm cortical response to song. If replicated, the result argues for deliberately including fathers and male voices in NICU music and family-centered care, which remain built largely around the mother.