Use sd card

Solution
Is there another tune in the same folder? Once a track has been played, the system can't get back inside a folder to play the next so I copy them and paste them outside the folder. Move them into your PC to organise them then ship them back to the phone.
It should be no different from music stored anywhere else. Plug your earbuds in and use your File Manager to navigate to the card.

Find the music folder, open it and double click on a track and it should play.
 

I've downloaded a file. Manager app it only let me play one song and then I have to go back to the phone to play another one
 
Is there another tune in the same folder? Once a track has been played, the system can't get back inside a folder to play the next so I copy them and paste them outside the folder. Move them into your PC to organise them then ship them back to the phone.
 
Solution