Musical expectations modulate declarative memory formation.

Music elicits powerful engagement through the generation and resolution of expectations, yet its effects on declarative memory formation remain unclear. Using predictive processing frameworks, we examined whether harmonic expectancy and prediction error modulate memory formation for concurrently presented visual stimuli. Participants listened to Bach chorales in which musical instruments probabilistically predicted consonant or dissonant endings, generating distinct expectations of outcomes. Neutral images were presented both before and after the critical musical period, and memory was tested 24 h later. At the period where the music either changed to dissonant or remained consonant, participants were prompted to rate whether the music was pleasant or unpleasant at that time. Participants showed robust sensitivity to harmonic structure, rating consonant endings as pleasant and responding faster to dissonant endings. Critically, unsigned prediction error magnitude positively predicted subsequent recognition accuracy and confidence. Whereas the relationship between prediction error and recognition accuracy did not reliably differ across temporal periods, its relationship with confidence was significantly stronger for images encoded in the anticipatory period preceding the musical transition. These findings indicate that musical expectations modulate declarative memory, with temporal specificity evident for subjective confidence, suggesting that prediction-related processes gate episodic encoding in a graded, time-dependent manner.