(go to Creating a System for Intersecting State Areas)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SetMusicState : MonoBehaviour {
    public static List<AK.Wwise.State> ListOfStates = new List<AK.Wwise.State>();
    public AK.Wwise.State OnTriggerEnterState;
    public AK.Wwise.State OnTriggerExitState;
    private void OnTriggerEnter(Collider other){
        if(other.CompareTag("Player")){
            ListOfStates.Insert(0, OnTriggerEnterState);
            ListOfStates[0].SetValue();
        }
    }
    private void OnTriggerExit(Collider other){
        if(other.CompareTag("Player")){
            ListOfStates.Remove(OnTriggerEnterState);
            if(ListOfStates.Count > 0){
                ListOfStates[0].SetValue();
            }
	        else{
                OnTriggerExitState.SetValue();
            }
        }
    }
}