Changes of EEG during listening to music were studied in two groups of probands, one of them with several years of training on a musical instrument. The EEG was recorded simultaneously from 19 electrodes (10:20 system) against connected ear lobe electrodes. One minute recording periods at rest before and after music were compared with a period of one minute recording during listening to music. 30 seconds of each of these recordings were studied by Fourier analysis. Averaged power and coherence spectra (between transversally adjacent electrodes and between electrodes on homologous regions of both hemispheres) were computed. Broad band parameters were chosen for 5 frequency bands between 4 and 32 Hz. Significant changes of the parameters were represented topographically. During listening to music, a significant reversible decrease of the parameters studied was found: in the musically trained group on both sides, but preponderantly on the right hemisphere, in the non-trained group almost exclusively on the left hemisphere. Moreover, in the trained group, the changes occurred more frequently and involved larger regions of the skull than in the untrained group. In addition, the first group had most changes in the frequency range between 18 and 24 Hz, the second group between 13 and 18 Hz. Finally, comparisons of the changes between the control period before music and music and those between the control period after music and listening to music led to additional conclusions on different strategies of the processing of musical information in musically trained and untrained persons.