The Resonalyser is designed for analyzing the orthotropic elastic properties (engineering constants: Young’s moduli E1 and E2, Poisson’s ratio ν12 and the in-plane shear modulus G12) of rectangular beams and test plates. The Resonalyser procedure is based on the inverse method to measure the resonance frequencies of test plates by IET and to compare these measurements with computed values by accurate finite element models. The engineering constants in the finite element models are tuned in such a way that the computed vibration behavior matches the measured vibration behavior as close as possible. This method is fast and yields very accurate results. The user-friendly interface allows an easy interpretation and logging of the results.