比较简单，只有三个类，参考了其他代码并修改了下:
AppDelegate类修改的比较少.
AppDelegate.cpp:

#include "AppDelegate.h"
#include "MainMenu.h"
#include "SimpleAudioEngine.h"
USING_NS_CC;
using namespace CocosDenshion;
AppDelegate::AppDelegate() {

}

AppDelegate::~AppDelegate() 
{
}

bool AppDelegate::applicationDidFinishLaunching() {
    // initialize director
    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();
    if(!glview) {
        glview = GLViewImpl::create("My Game");
        director->setOpenGLView(glview);
    }

    // turn on display FPS
    director->setDisplayStats(false);

    // set FPS. the default value is 1.0/60 if you don't call this
    director->setAnimationInterval(1.0 / 60);

    // create a scene. it's an autorelease object
    auto scene = MainMenu::createScene();

    // run
    director->runWithScene(scene);
    //开始播放背景音乐
    SimpleAudioEngine::getInstance()->playBackgroundMusic("background.mp3",true);//重复播放

    return true;
}

// This function will be called when the app is inactive. When comes a phone call,it's be invoked too
void AppDelegate::applicationDidEnterBackground() {
    Director::getInstance()->stopAnimation();

    // if you use SimpleAudioEngine,it must be pause
    SimpleAudioEngine::getInstance()->pauseBackgroundMusic();
}

// this function will be called when the app is active again
void AppDelegate::applicationWillEnterForeground() {
    Director::getInstance()->startAnimation();

    // if you use SimpleAudioEngine,it must resume here
    SimpleAudioEngine::getInstance()->resumeBackgroundMusic();
}