SimpleSoundManager.cs

using UnityEngine;

public class SimpleSoundManager:MonoBehaviour {
    // Audio source
    private AudioSource musicSrc;
    private AudioSource effectSrc;
    // Instance variable
    private static SimpleSoundManager instance;

    // Instance
    public static SimpleSoundManager I {
        get {
            if(instance == null && Application.isPlaying) {
                // Create container gameobject
                GameObject smc = new GameObject("SimpleSoundManagerContainer");
                DontDestroyOnLoad(smc); // Persist
                // Add sound manager as component
                instance = smc.AddComponent<SimpleSoundManager>();
            }
            return instance;
        }
    }

    // Volume
    public float MusicVolume {
        get { return musicSrc.volume; }
        set { musicSrc.volume = value; }
    }

    public float EffectVolume {
        get { return effectSrc.volume; }
        set { effectSrc.volume = value; }
    }

    // Init audio sources
    public void Awake() {
        // Add audio sources
        musicSrc = gameObject.AddComponent<AudioSource>();
        effectSrc = gameObject.AddComponent<AudioSource>();
        // Set volumes
        EffectVolume = MusicVolume = 1f;
    }

    /*********************** EFFECTS & MUSIC ****************************/

    // Single Effect
    public void PlayEffectOnce(AudioClip snd) {
        effectSrc.PlayOneShot(snd);
    }

    // Random Effect from list
    public void PlayEffectOnce(AudioClip[] snds) {
        if(snds.Length > 0)
            PlayEffectOnce(snds[Random.Range(0, snds.Length)]);
    }

    // Music
    public void PlayMusic(AudioClip snd, bool loop) {
        musicSrc.clip = snd;
        musicSrc.loop = loop;
        musicSrc.Play();
    }

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