How to lower the volume of my BGM

Unity Engine
1

I want to lower the volume of my BGM that is on DontDestroyOnLoad on the next scene on Start without a slider?

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

public class BG : MonoBehaviour
{
    private static BG instance = null;
    public static BG Instance
    {
        get { return instance; }
    }
    private void Awake()
    {
        if(instance != null && instance != this)
        {
            Destroy(this.gameObject);
                return;
        }
        else
        {
            instance = this;
        }
        DontDestroyOnLoad(this.gameObject);
    }
}
2

The code you posted doesn’t appear to have anything to do with playing music, and if you don’t want to use a slider you might want to state what you do want to use.

But most likely just setting the music AudioSource’s volume to whatever you want is what you’re looking for.