Import sound file, drag in scene
Set in Details that unable Allow Spatialation (2D music, same volume) and Auto Activate
Reset the sound file
In Level BP, set as follow by Create a reference of the music file in the scene
Now choose the music originally from the music file
Fade in time to let the transition
Change music in trigger:
Create a trigger box in the scene, select on it and go to Level BP again
Add on actor being/overlap
Duplicate the nodes as before, then put the new nodes as below to connect the trigger node:
Change the music in Set Sound node
Or just connect the begin overlap node directly to Set Sound node