How to change volume between 2 tracks without resetting via triggerbox?

I’m trying to create a system that plays 2 music tracks that are similar at the same time, but keeps one of them muted until the player character enters a triggerbox, which would cause the 2 tracks to fade in and out until said box is left, so far I managed to get both tracks to play:


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I already had this partly solved but I somehow lost my progress on the level blueprint (which should handle the volume switching) so now I am lost again with 3 issues:

  • How do I change the level blueprint to change the volumes of the tracks while the character is inside the triggerbox?
  • How do I prevent the music tracks from restarting everytime I enter or leave the triggerbox?
  • How do I make it so the tracks fade in and out with the volume changes?