Apps Setting Ringtone from MP3 on SD Card

[derrickorama]

I've been trying to find the correct way to set the ringtone (or notification tone) using a file on the SD card. Basically all I found was this:

Settings.System.putString(
	MyApp.this.getContentResolver(), 
	Settings.System.RINGTONE,
	"/sdcard/mydir/ringTone.mp3"
);

I know that the file is there, I know that it is valid, it even returns "true" when I check to see if it set the ringtone. But it doesn't play the MP3. Is there something more I have to do to set the ringtone? Is there some other code I can use?

Thanks