Okay so I saw your YouTube demonstration and understand what you’re trying to do.
In your wave spawner Blueprint, you’re going to want to create an Event Dispatcher and name it something like PlayWaveMusic. Add an input to the event dispatcher so you can tell your music system which wave has started, this could be the row name from the data table.
Then, drag the event dispatcher into your wave spawner graph and choose “Call” from the listed options. Connect the event dispatcher call to whatever event is starting the wave, and feed the row name into the dispatcher’s input.
Then drag the event dispatcher from your wave spawner blueprint over to your music system blueprint. This time, choose “Event.” Now you have an event that will fire each time the event dispatcher is called and you will be able to get the row name. [Edit: I forgot to mention binding the event before doing this, I will explain when I get back.]
This is where it’ll get a bit tricky with how your system is set up.
The easiest way to go from here would be to have all of your layers in the same sound cue (assuming you’re on UE4) so you only have one audio component to manage. Your sound cue would have each of the layers in its own wave player, connected to a continuous modulator, then all of them combined in a mixer node before hitting the output.
On the continuous modulator you would set the name of the volume modulation parameter to be the same as the data table’s row name.
Then back in your music system blueprint, you would use Set Float Parameter using the data table row name as the input name, then lerp in your volume fade.
I gotta run right now so I apologize for not including screenshots, but this is one way it could work.