A novel digital signal processing method is presented for isolating the vibrational resonances of rotor components from engine tachometer signals. Speed Clock resampling removes spectral leakage and spreading. Sideband manipulation removes AM signal components. Spectral addition removes translational FM components. Sideband multiplying and averaging removes random noise. The result is a spectrum of high resolution and dynamic range comprised of isolated engine rotor resonances, which can be used to track health and performance in engines and other turbomachines.