How to use external audio file in Android application? ,How to read external audio files on Android?

Making an audio player for Android on Unity. Question: how to make so that the program can use audiofile stored on the device and not upload them in advance in Unity itself? And if it is possible, is it possible to implement it in such a way that the audilfiles can be simply thrown into one folder, and inside the application to specify its directory from a mobile device? (preferably without plugins, but if nothing else left, it is better than nothing)