Professional musicians worldwide suffer from hearing loss as an occupational disease. Though among musicians permanent threshold shifts occur frequently, they are able to play music without problems. Therefore we assume that changes in the central processing of auditory signals reflecting functional reorganization could be detected by the analysis of mismatch negativity (MMN). Classical orchestral music can induce hearing damage, since sound intensities >85 dB SPL are often produced during rehearsals in small rooms. Intensities >120 db SPL are measured in the orchestra pit during performances. Training times >500 hrs. per year additionally increase the risk of PTS. We recorded tone audiograms and otoacoustic emissions from 172 professional musicians aged 11-69 years. To study the perception of auditory attributes in normal hearing vs. hearing impaired musicians and in musicians vs. non-musicians we recorded MMN from auditory evoked fields stimulated with pure sharp major chords and out of tune chords in a classical oddball paradigm (65-70 dB SPL, standard vs. deviant 1:4, randomized occurrence) by EEG and MEG. Even hearing impaired professional musicians recognized disturbed tones better than normal hearing non- musicians, as indicated by larger MMN amplitudes. We assume therefore that central auditory processing is changed in the group of professional musicians trained to musical stimuli.