Since the turn of this century, a substantial body of research has been published on the neuroscience of creativity. Now, it is necessary to study the neurophysiological correlates in true-to-life, professionally specific situations. The aim of our empirical research was to study the neurophysiological correlates of musical improvisation, a spontaneous creative activity. The participants were 136 right-handed practicing musicians aged 19 to 36 (102 males and 34 females), divided into two groups-professionals (56 people) and amateurs (80 people). EEG signals were recorded in a resting state (eyes closed) and during three types of internal musical activity (perceiving, mentally reproducing, and mentally improvising) from 21 scalp electrodes according to the International 10-20 System. For statistical analysis, we used ANOVA and post hoc analysis. For the main neurophysiological correlates of musical creativity, we revealed higher values of EEG spectral power in the delta band and the dominance of long-distance functional cortical connections in the high-frequency bands. Variable neurophysiological correlates were differentiated according to emotions and the professional level of the musicians. The distinguishing EEG pattern in the professional musicians during improvisation was the predominant activation of the lefthemisphere cortical regions simultaneously with high interhemispheric integration in the high-frequency band along the "creativity axis. " The revealed neurophysiological correlates of musical creativity during improvisation included basic and variable components and were characterized by a specific frequency-spatial organization of bioelectric cortical activity in the musicians.