Assessing properly phase synchrony is a real challenge, even for offline analysis. It has mostly to do with the volume conduction / volume leakage mixing , the uncertainty principle and the redundancy of the wavelet coefficients. One or more of these issues are often neglected. We provide a framework for better understanding and interpreting phase extraction with the Morlet Wavelet Transform to show that errors are made when extracting phase information and must be accounted for. Before attempting to blindly use phase synchrony measures in Neurofeedback, there a fortiori a need for a proper and efficient estimation of the statistical significance of the measures calculated on the fly.