How can I make the background music fade out after timer hits 0 ?

Unity Engine
,
1

Hi, I would like to know how can I make the background music fade out after timer is 00:00 ?
How can I add that to this script ?
This is my timer script.

using UnityEngine;
using TMPro;
using UnityEngine.SceneManagement;
using System.Collections;

public class TimerManagerScript : MonoBehaviour
{
    public float timeLeft;
    public bool timerOn = false;
    public GameObject player;
    private bool stopMovement;

    public TMP_Text timerTxt;
    void Start()
    {
        stopMovement = GameObject.Find("Player").GetComponent<PlayerMovement>().enabled;
        timerOn = true;
    }

    void Update()
    {
        timerCheck();
    }

    public void timerCheck()
    {
        if (timerOn)
        {
            if (timeLeft > 0)
            {
                timeLeft -= Time.deltaTime;
                updateTimer(timeLeft);
            }
            else
            {
                timeLeft = 0;
                timerOn = false;
                timerTxt.color = Color.red;
                Destroy(player);
                stopMovement = false;
                StartCoroutine(ResetLevel());
            }
        }
    }

    public void updateTimer(float currentTime)
    {
        currentTime += 1;

        float minutes = Mathf.FloorToInt(currentTime / 60);
        float seconds = Mathf.FloorToInt(currentTime % 60);

        timerTxt.text = string.Format("{0:00}:{1:00}", minutes, seconds);
    }

    IEnumerator ResetLevel()
    {
        yield return new WaitForSeconds(2);
        SceneManager.LoadScene(SceneManager.GetActiveScene().name);
    }
}
2

I see two simple ways to do that:

When timerCheck() could return a bool, and when it’s true you could gradually lower the volume of a specific AudioSource. Ideally I would run that in FixedUpdate to have a smoother fade out.

void FixedUpdate()
{
    if (timerFinished())
    {
        if ((audioSource.volume *= fadeRate) < 0.01)
        {
            audioSource.Stop(); // or disable it
            // any relevant trigger or callback
        }
    }
}

Also you could leverage the AudioMixer and use Snapshots to dial down your music channel. Here’s a good tutorial on the matter: