C++ 使用MIDI库演奏《晴天》

那些在MIDI库里徘徊的十六分音符

终究没能拼成告白的主歌

我把周杰伦的《晴天》写成C++的类
在每个midiEvent里埋藏故事的小黄花

调试器的断点比初恋更漫长
而青春不过是一串未导出的cmake工程文件

在堆栈溢出的夜晚
终将明白
有些旋律永远停在#pragma once的注释里
有些人永远停在未定义的引用里

或许你我的心跳终归运行在不同的时钟频率
却愿始终记得如何编译出一场永不落幕的晴天

　　　　　　　　　　　　　　　　　　--题记

就像在题记里说的一样，这是一个从未导出成功的工程文件。
所以如果你也想听听，可以在PowerShell里运行以下指令：

git clone https://github.com/TwilightLemon/SunnyDays

cd SunnyDays

mkdir build

cd build

cmake .. -G "MinGW Makefiles"

mingw32-make

./SunnyDays.exe

没环境？巧了，她也如是说。

幸运的话能得到以下效果：

下面来简单讲讲如何使用C++和MIDI库作曲吧。

一、开始工作

1. 引入MIDI库和相关控制类

在CMakeLists.txt中：

target_link_libraries(SunnyDays winmm)

在MIDIHelper.h中：

#include <windows.h>

#pragma comment(lib,"winmm.lib")

定义Scale(音阶), Instrument(乐器, 仅包括部分)等枚举。我把Drum单独提了出来。

enum Scale

{

    X1 = 36, X2 = 38, X3 = 40, X4 = 41, X5 = 43, X6 = 45, X7 = 47,

    L1 = 48, L2 = 50, L3 = 52, L4 = 53, L5 = 55, L6 = 57, L7 = 59,

    M1 = 60, M2 = 62, M3 = 64, M4 = 65, M5 = 67, M6 = 69, M7 = 71,

    H1 = 72, H2 = 74, H3 = 76, H4 = 77, H5 = 79, H6 = 81, H7 = 83,

    LOW_SPEED = 500, MIDDLE_SPEED = 400, HIGH_SPEED = 300,

    _ = 0XFF

};

enum Drum{

    BassDrum = 36, SnareDrum = 38, ClosedHiHat = 42, OpenHiHat = 46

};

enum Instrument{

    AcousticGrandPiano = 0, BrightAcousticPiano = 1,

    ElectricGrandPiano = 2, HonkyTonkPiano = 3,

    ElectricPiano1 = 4, ElectricPiano2 = 5

};

一些基础方法，包括初始化/关闭设备、设置参数、播放单个音符和播放和弦等。

void initDevice();

void closeDevice();

void setInstrument(int channel, int instrument);

void setVolume(int channel, int volume);

void PlayNote(HMIDIOUT handle, UINT channel, UINT note, UINT velocity);

void playChord(HMIDIOUT handle, UINT channel, UINT note1, UINT note2, UINT note3, UINT note4, UINT velocity);

void playChord(HMIDIOUT handle, UINT channel, UINT note1, UINT note2, UINT note3, UINT velocity);

在MIDIHelper.cpp中：

void initDevice(){

    midiOutOpen(&hMidiOut, 0, 0, 0, CALLBACK_NULL);

}

void closeDevice(){

    midiOutClose(hMidiOut);

}

void setInstrument(int channel,int instrument){

    if (channel > 15 || instrument > 127) return;

    DWORD message = 0xC0 | channel | (instrument << 8);

    midiOutShortMsg(hMidiOut, message);

}

void setVolume(int channel,int volume){

    if (channel > 15 || volume > 127) return;

    DWORD message = 0xB0 | channel | (7 << 8) | (volume << 16);

    midiOutShortMsg(hMidiOut, message);

}

//播放单个音符，note是音符，velocity是力度

void PlayNote(HMIDIOUT handle, UINT channel, UINT note, UINT velocity) {

    if (channel > 15 || note > 127 || velocity > 127) return;

    DWORD message = 0x90 | channel | (note << 8) | (velocity << 16);

    midiOutShortMsg(handle, message);

}

//四指和弦

void playChord(HMIDIOUT handle, UINT channel, UINT note1, UINT note2, UINT note3, UINT note4, UINT velocity){

    if (channel > 15 || note1 > 127 || note2 > 127 || note3 > 127 || note4 > 127 || velocity > 127) return;

    DWORD message1 = 0x90 | channel | (note1 << 8) | (velocity << 16);

    DWORD message2 = 0x90 | channel | (note2 << 8) | (velocity << 16);

    DWORD message3 = 0x90 | channel | (note3 << 8) | (velocity << 16);

    DWORD message4 = 0x90 | channel | (note4 << 8) | (velocity << 16);

    midiOutShortMsg(handle, message1);

    midiOutShortMsg(handle, message2);

    midiOutShortMsg(handle, message3);

    midiOutShortMsg(handle, message4);

}

//三指和弦

void playChord(HMIDIOUT handle, UINT channel, UINT note1, UINT note2, UINT note3, UINT velocity) {

    if (channel > 15 || note1 > 127 || note2 > 127 || note3 > 127 || velocity > 127) return;

    DWORD message1 = 0x90 | channel | (note1 << 8) | (velocity << 16);

    DWORD message2 = 0x90 | channel | (note2 << 8) | (velocity << 16);

    DWORD message3 = 0x90 | channel | (note3 << 8) | (velocity << 16);

    midiOutShortMsg(handle, message1);

    midiOutShortMsg(handle, message2);

    midiOutShortMsg(handle, message3);

}

2. 初始化和结束

先在头文件中定义一个全局MIDI句柄:

extern HMIDIOUT hMidiOut;

在入口处初始化MIDI设备并在结束时关闭：

HMIDIOUT hMidiOut;

int main() {

    initDevice();

    //...

    closeDevice();

    return 0;

}

初始化MIDI设备之后，为每一个乐器分配一个通道channel（0~15，通常9分配给打击类乐器,例如鼓组），控制音量volume，然后就可以开始演奏了。

二、自制简易乐谱

以Voice.cpp为例,定义一个数组为频谱，控制停顿和音符，遍历数组播放：

 1 namespace SunnyDays{

 2     int channelVoice=1;

 3     void playVoice(int note, int velocity){

 4         PlayNote(hMidiOut, channelVoice, note, velocity);

 5     }

 6     void voice(){

 7         Sleep(13100);//等待前奏

 8         int sleep = 390;

 9         int data[] =

10                 {

11                     //故事的小黄花

12                     -90,

13                     300,M5,M5,M1,M1,_,M2,M3,_,

14                     //从出生那年就飘着

15                     -90,

16                     M5,M5,M1,M1,0,M2,M3,300,M2,M1,_,

17                     //童年的荡秋千

18                     -90,

19                     300,M5,M5,M1,M1,_,M2,M3,_,

20                     //随记忆一直晃到现在

21                     -90,

22                     M3,_,500,M2,M3,M4,M3,M2,M4,M3,700,M2,700,_,

23                     //...

24                 }

25         for (auto i : data) {

26             if(i==-30){logTime("Enter chorus");continue;}//调试用

27             if(i==-90){NextLyric(); continue;}

28             if (i == 0) { sleep = 180; continue; }

29             //...

30             if (i == _) {

31                 Sleep(390);

32                 continue;

33             }

34

35             playVoice(i, 80);

36             Sleep(sleep);

37         }

38     }

39 }

打个鼓：

 1 namespace SunnyDays{

 2     int channelBassDrum=9;

 3

 4     void playDrum(int note, int velocity, int duration){

 5         PlayNote(hMidiOut, channelBassDrum, note, velocity);

 6         if(duration>0) {

 7             Sleep(duration);

 8             PlayNote(hMidiOut, channelBassDrum, note, 0);

 9         }

10     }

11

12     void bassDrum(){

13         Sleep(11260);

14         cout<<"Drum Bass Start!"<<endl;

15         playDrum(SnareDrum,100,180);

16         playDrum(SnareDrum,100,210);

17         playDrum(BassDrum, 100, 210);

18         playDrum(SnareDrum,100,190);

19         playDrum(BassDrum, 100, 210);

20         playDrum(SnareDrum,100,200);

21         playDrum(SnareDrum,100,200);

22         playDrum(OpenHiHat,100,-1);

23         Sleep(200);

24         //...

25     }

26 }

简易副歌和弦，是从B站一位up主那里学的（已经忘记是哪位了qwq）：

 1 namespace SunnyDays {

 2     int channelChord=2;

 3     void chordLevel(int level,int sleep,int repeat=2,int vel=70){

 4         repeat--;

 5         int down=8;

 6         if(level==1){

 7             //一级和弦 加右指

 8             playChord(hMidiOut, channelChord, M1, M3, M5, L1, vel);

 9             while(repeat--) {

10                 Sleep(sleep);

11                 playChord(hMidiOut, channelChord, M1, M3, M5, vel - down);

12             }

13         }else if(level==3){

14             //三级和弦 加右指

15             playChord(hMidiOut, channelChord, M3, M5, M7, L3, vel);

16             while(repeat--) {

17                 Sleep(sleep);

18                 playChord(hMidiOut, channelChord, M3, M5, M7, vel - down);

19             }

20         }

21         //...

22     }

23     void chord(){

24         Sleep(63724);

25         int sleep=740;

26         int data[]={

27                 //刮风这天 我试过握着你手

28                 1,4,

29                 6,4,

30                 //但偏偏 雨渐渐

31                 4,2,

32                 5,2,

33                 //大到我看你不见

34                 1,4,

35                 //还有多久 我才能

36                 3,4,

37                 //↑ 在你身边

38                 6,4,

39                 //↓ 等到放晴的那天

40                 4,4,

41                 //↑ 也许我会比较好一点

42                 5,4,

43                 //..

44         }

45         int count=sizeof(data)/sizeof(int);

46         for(int i=0;i<count;i+=2){

47             cout<<"chord "<<data[i]<<"  x"<<data[i+1]<<endl;

48             chordLevel(data[i],sleep,data[i+1]);

49             Sleep(sleep);

50         }

51         //...

52     }

53 }

三、合成演奏

我用了一个笨蛋方法，用多线程单独控制每一个通道，然后在主线程中调用：

 1 int main(){

 2     //...

 3     initDevice();

 4     //设置音量

 5     setVolume(channelChord,80);

 6     setVolume(channelMainLine,80);

 7     setVolume(channelVoice,120);

 8     setVolume(channelBassDrum,80);

 9

10     //设置乐器（特定音色）

11     setInstrument(channelChord,ElectricPiano1);

12     setInstrument(channelMainLine,ElectricPiano1);

13

14

15     system("pause");//按下回车，就开始啦

16     beginLogger();

17

18

19     thread t0(voice);

20     thread t1(mainLine);

21     thread t2(bassDrum);

22     thread t3(chord);

23     t0.join();

24     t1.join();

25     t2.join();

26     t3.join();

27

28     closeDevice();

29     //...

30 }

（最后叠个甲，俺不懂音乐制作，更不会什么C++）

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