Based on this example https://www.b4x.com/android/forum/threads/background-playback.49337/ I've implemented background sound playing, which works as expected.
The only thing missing is the display of the Author/Song title in the On Screen Control
the MP3 file has "Author", "Title", "Album" and "Track" tags are correctly set.
Tags are both in ID3 V1.0 and V2.3 format
Here is the code:
B4X:
VP_background.ShowControls = False
VP_background.LoadVideo(File.DirAssets, "backgroundsound.mp3")
Wait For VP_background_Ready (Success As Boolean)
Dim NativeMe As NativeObject= Me
NativeMe.RunMethod("setAudioSession", Null)
NativeMe.RunMethod("register", Null)
VP_background.Play