Abstract <p>A method for exploratory data analysis intended to reveal regularities in twin electromyographic signals is developed. The method allows detecting frequency ranges in which the instantaneous phase of signals under study demonstrates neurophysiological regularities with a diagnostic value. In addition to that, the method allows finding the optimal relation between the contribution of phase and amplitude characteristics of the signal in searching for neurophysiological regularities. The developed method allows revealing new neurophysiological regularities in electromyographic signals of antagonistic muscles in patients with Parkinson’s disease and patients with essential tremor. Ten patients with Parkinson’s disease with trembling hyperkinesis of the left hand, 12 patients with Parkinson’s disease with trembling hyperkinesis of the right hand, and 13 patients with essential tremor with trembling hyperkinesis of both hands were surveyed. The results of the study confirm the presence of differences in clinical aspects and the ways that trembling hyperkinesis appears in patients with Parkinson’s disease with trembling hyperkinesis of the left or right side of the body. The revealed regularities are applied to differential diagnosis of Parkinson’s disease and essential tremor.</p>