Gait disorders are a primary consequence of Parkinson's Disease (PD), resulting in loss of patients' independence. Recently, Rhythmical Auditory Stimulation (RAS) gave a preliminary proof to benefit gait quality, but the specific methodology requires a long walkway, preventing the use of a traditional complete gait analysis. In the present work we describe an unobtrusive, wearable setup and the related biomechanical model developed for analyzing gait of people with PD during the administration of RAS. One healthy subject was enrolled in the experimental session to validate the estimation of the spatial gait parameters provided by the proposed setup, against an optoelectronic system. Three PD patients were then enrolled to test the setup feasibility in evaluating gait parameters typically adopted in these type of studies. Results related to the validation of the spatial parameter estimation showed a high accuracy of the system in the estimation of the stride length. Preliminary tests on PD patients provided encouraging insights on the wearable setup usability and versatility. Future experimental validation on a larger population will be conducted to fully validate the setup, which opens the way for conducting RAS studies also outside the laboratory environment.