You can compare the LayoutName value in an event with the System->Compare two values condition then set the music to play based on that.
Or if you really want to cut down on events, in an existing event you might have like On start of layout, add the Audio->Play by name action with the name set to:
LayoutName = "Layout 1" ? "L1 Music" : "L2 Music"
Obviously change the names to whatever you're actually using.
You can also expand that if you add more layouts:
LayoutName = "Layout 1" ? "L1 Music" : LayoutName = "Layout 2" ? "L2 Music" : "L3 Music"
Edit: Actually you can simplify things by naming your music the same as your layouts and just setting Audio->Play by name to LayoutName