In order to read the audio files on the device, the code does a query of the MediaStore. I'm not sure how often that MediaStore updates the indexed results - it sounds like it doesn't update all that often based on your description. It's not really something I have control over unfortunately. If you move the audio files around frequently, it may be faster to update things on the tablet itself. Allowing the companion app to browse the file system on the Android device over WiFi is beyond the current scope of what is supported.
Mike
Mike