music when close to something

well if you have a reference to the transform of the player, and the transform of the thing they need to get close to you can use a line like

 Vector3.Distance(playerTransform.position, thingTransform.position);

and that will give you the distance as a float between those 2 objects. then you can say something like

 AudioSource source;
 float maxDistance = 5f;
 
 
 private void SetMusicVolume(float distance)
 {
     distance = Mathf.Clamp(distance, 0f, maxDistance);
     source.volume = Mathf.lerp(1f, 0f, distance/maxDistance);
 }

in order to set the volume based on that distance. then you would just have to call that function however often in order to make it actually reactive to the player distance. I would try not to just call it from update since that would get expensive if you had a bunch of these, but using update would probably be the fastest way to make it work.