Processing western tonal music may yield distinct brain responses depending on the mode of the musical compositions. Although subjective feelings in response to major and minor mode are well described, the underlying brain mechanisms and their development with increasing expertise have not been thoroughly examined. Using high-density electroencephalography, the present study investigated neuronal activities in the frequency domain in response to polyphone musical compositions in major and minor mode in non-musicians, amateurs and experts. During active listening decrease of theta- and gamma-frequency range activities occurred with increasing expertise in right posterior regions, possibly reflecting enhanced processing efficiency. Moreover, minor and major compositions distinctively modulated synchronization of neuronal activities in high frequency ranges (beta and gamma) in frontal regions, with increased activity in response to minor compositions in musicians and in experts in particular. These results suggest that high-frequency electroencephalographic (EEG) activities carry information about musical mode, showing gradual increase of processing efficiency and sensitivity with musical expertise.