private PlaySound SpawnBlackKey(int setID, int soundKeyID, PlaySound.SoundKey targetSoundKey)
    {
        float      zOffset  = offset * setID + soundKeyID * 0.5f;
        Vector3    position = new Vector3(0, 0.3f, zOffset);
        GameObject blackKey = Instantiate(BlackKeyPrefab, position, Quaternion.identity, transform);

        PlaySound playSound = blackKey.GetComponentInChildren <PlaySound>();

        playSound.pitchOffset = setID;
        playSound.soundKey    = targetSoundKey;
        playSound.LoadAudioClip();
        return(playSound);
    }