The Rossi X-ray timing explorer, which operated from 1995 to 2012, has provided a large amount of NS data. Timing analysis of the X-ray flux in more than a dozen NS systems reveals remarkable correlations between frequencies of two characteristic peaks present in the high-frequency part of the power-density spectra. We discuss a simple analytic relation that well reproduces these correlations. We outline a possible physical interpretation of the relation's parameters and explore the impact of the obtained results in a broader context.