I tried moving all the Music files into Sound folder. I am not sure the "side effect" doing this. Maybe someone can explain, if there is any side effect. All background musics play well on my android now. No delay at all.
This is what I do:
1. Make sure the Preload Sounds property is set to Yes.
2. EVENT: System: On start of Layout > Audio: Play <sound name>
No need to use the Preload sound action.
I hope this help