The present invention relates to a system and a method for selecting an audio file using motion data from a mobile computing device connected to or held by a user, the mobile computing device comprising or coupled to motion sensors. The method comprising steps of moving the mobile computing device, obtaining motion data from the motion sensors, computing from the motion data step data based on a number of steps taken by the user in a specific period of time, computing a metronome beat based on the step data and generating a metronome beat file, selecting a stored audio file having a predefined beat parameter matching the metronome beat of the metronome beat file, and playing the audio file. The present invention provides a technology solution delivered through a mobile computing device, such as smart phone, or other computing device, such as a laptop or a PC, a wrist or smart watch, or an accelerometer, pedometer or other external computing device having computer processor means, that improves the gait of people with Parkinson's disease. In use, the user's daily mobility is assessed through application software on a mobile computing device which is operable to calculate a required individually prescribed treatment for a user. The treatment is then delivered through speakers of the mobile computing device in the form of metronome therapy which is form of auditory cueing that is used to treat people with Parkinson's disease.