Finding non-linearity is a common application of modal testing but in this way, there is a need to control the input signal. Nowadays, commercial data acquisition software is not enough flexible in controlling the applied signals, whereas MATLAB as general software which supports National Instrument makes it possible to run modal test and control input signal via closed-loop controlling. In this work, using MATLAB commands, a modal test is run with a stepped-sine excitation and the input is controlled to achieve desired pure sinusoidal excitation which commonly is used in finding the non-linearity.