MusicManager.cs
using Sandbox;

public class MusicManager : Component
{
    public static MusicManager Instance { get; private set; }

    [Property] public SoundEvent MusicSound { get; set; }

    private SoundHandle _musicHandle;

    protected override void OnStart()
    {
        Instance = this;

        if ( PushHud.EnableMusic )
        {
            PlayMusic();
        }
    }

    public void ToggleMusic( bool enable )
    {
        if ( enable )
        {
            PlayMusic();
        }
        else
        {
            StopMusic();
        }
    }

    public void PlayMusic()
    {
        if ( _musicHandle.IsValid() ) return;

        if ( MusicSound != null )
        {
            _musicHandle = Sound.Play( MusicSound );
        }
    }

    public void StopMusic()
    {
        if ( _musicHandle.IsValid() )
        {
            _musicHandle.Stop();
        }
    }
}