How do you fade out 2D background music when 3D music from an object fades in?

I have 2D background music playing throughout the game, but when you go near certain objects, I have attached a 3D audio source, so it fades in and out when you go near and away from the object.

T$$anonymous$$s is fine except the 2D background music continues to play and it clashes.

Is it possible to make the background music fade out when the 3D music fades in and vice versa?