Coupling experimental and simulation models is applied where accurate prediction of vibrations is necessary early in the development process. Whenever excitation with correct amplitudes is of interest, real time coupling is a promising technique. The use of adaptive feed-forward filters allows robust real-time coupling of virtual and experimental components for periodic excitations. In this contribution, we present an approach with harmonic basis functions based on a Recursive Least Squares (RLS) adaption law. An experimental validation of the approach is performed on a beam test rig with two degrees of freedom (DoF). The results show that the approach offers correct coupling in a broad frequency range for multiple DoF interfaces as well as fast convergence without prior knowledge of the system dynamics. Hence, we consider this contribution a step toward the practical application of the method in the field of Noise- Vibration-Harshness (NVH) engineering.