Functional Impact of Increasing Minor Intervals in North Indian Classical Music on Cortical Sources and Emotional Responses

Background: North Indian classical music ragas evoke distinct emotional responses, shaped by their tonal structures. Prior studies on Western music have shown that minor and major intervals influence affective valence and neural activity, but similar research in the Indian context is limited. Purpose: This study aimed to investigate how increasing minor-to-major intervals (m/M tonal ratios) in North Indian classical music affect cortical sources and emotional responses. Methods: Thirty healthy participants listened to four ragas-Bilawal (M1), Yaman (M2), Puriya Kalyan (M3), and Todi (M4)-while undergoing EEG recording. Emotional responses were assessed using the GEMS-25 and self-assessment manikin (SAM) scales. The ragas were selected to represent ascending m/M tonal ratios. Results: Ragas with higher proportions of major intervals (e.g., Bilawal) elicited positive emotions such as joy and calmness, accompanied by widespread cortical activation, particularly in areas associated with emotional processing and musical familiarity. In contrast, ragas with increasing minor intervals (e.g., Todi) induced negative affect such as sadness and tension, with reduced cortical engagement. Raga Todi showed minimal deviation from resting-state EEG, correlating with low arousal and negative valence. EEG analysis revealed heightened activation in areas involved in acoustic processing and the Default Mode Network during Bilawal, which progressively declined across Yaman, Puriya Kalyan, and Todi as the m/M ratio increased. Conclusion: The minor-to-major tonal ratio significantly modulates emotional and cortical responses in Indian classical music. Increasing minor intervals reduces cortical engagement and evokes negative affective states. These findings not only mirror trends observed in Western music but also highlight the cultural and therapeutic potential of ragas in emotional regulation and mental well-being.