After searching for solution, I have found from this link that it is possible to retrieve path like:
Using Resource Id
Syntax : android.resource://[package]/[resource_id]
Example : Uri.parse("android.resource://com.my.package/" + R.raw.mp3filename);
Which is exactly what I want. Problem is that, I'm using lolipop, and it does not work. When the package/resource is parsed, path from Uri.parse will be null. Is there other way around to write this, since in my Song class, I have only access to resourceId (R.raw.mp3filename).