...
[SerializeField] private AudioSource music1Source;
[SerializeField] private string introBGMusic;    
[SerializeField] private string levelBGMusic;   
...
public void PlayIntroMusic() {                
   PlayMusic(Resources.Load("Music/"+introBGMusic) as AudioClip);
}

public void PlayLevelMusic() {                
   PlayMusic(Resources.Load("Music/"+levelBGMusic) as AudioClip);
}

private void PlayMusic(AudioClip clip) {   
   music1Source.clip = clip;
   music1Source.Play();
}

public void StopMusic() {
   music1Source.Stop();
}
...
