BGM
  チャンネルA
  チャンネルB

SE(効果音)
  チャンネルC

.ファイル構成

│  main.c
│  Makefile
│  notes.c
│  notes.h
│  pitches.h
│  psg.c
│  psg.h
│  
└─.vscode
        c_cpp_properties.json
        launch.json
        tasks.json

main.c

#include <stdio.h>

#include "notes.h"
#include "psg.h"

void on_complete(uint8_t id);

void main() {
  printf("[right]: play se\n");
  printf("[left]:  stop se\n");
  printf("[up]:    play bgm\n");
  printf("[down]:  stop bgm\n");

  while (1) {
    uint16_t key = getk();
    if (key == 28) {
      // [->]
      play_se(p_se_1, BASE_BPM * 2, 15, 0, 1, on_complete);
    }
    if (key == 29) {
      // [<-]
      stop_se();
    }
    if (key == 30) {
      // [up]
      play_bgm(p_bgm_1, BASE_BPM, 15, -1, 0, NULL);
    }
    if (key == 31) {
      stop_bgm();
    }
  }
}

void on_complete(uint8_t id) { printf("%d ", id); }

Makefile.

# コンパイラとターゲット設定
ZCC = zcc +msx
TARGET = main.rom

# ソースとオブジェクト
SRCS = main.c psg.c notes.c
OBJS = $(SRCS:.c=.o)

# デフォルトターゲット
all: $(TARGET)

%.o: %.c
	$(ZCC) -c $< -o $@

# ROM生成
$(TARGET): $(OBJS)
	$(ZCC) -subtype=rom -create-app $(OBJS) -o $(TARGET)

# クリーンアップ
clean:
	del /Q $(OBJS) $(TARGET) *.bin

notes.c

#include "notes.h"

uint16_t bgm_1_a[] = {
    // 1
    PIT_C4, 8, PIT_C4, 8, PIT_C4, 8, PIT_E4, 8, PIT_A4, 8, PIT_A4, 8, PIT_A4, 8,
    PIT_NONE, 8,
    // 2
    PIT_D4, 8, PIT_D4, 8, PIT_D4, 8, PIT_F4, 8, PIT_G4, 8, PIT_G4, 8, PIT_G4, 8,
    PIT_NONE, 8,
    // 3
    PIT_NONE, 8, PIT_G4, 8, PIT_G4, 8, PIT_GS4, 8, PIT_A4, 8, PIT_A4, 8, PIT_A4,
    8, PIT_GS4, 8,
    // 4
    PIT_G4, 4, PIT_B4, 4, PIT_C5, 4, PIT_NONE, 4,
    // 5
    PIT_NONE, 8, PIT_G4, 8, PIT_G4, 8, PIT_F4, 8, PIT_E4, 8, PIT_E4, 8, PIT_E4,
    8, PIT_F4, 8,
    // 6
    PIT_G4, 8, PIT_G4, 8, PIT_G4, 8, PIT_G4, 8, PIT_C4, 8, PIT_NONE, 4,
    // 7
    PIT_NONE, 8, PIT_F4, 8, PIT_F4, 8, PIT_E4, 8, PIT_D4, 8, PIT_D4, 8, PIT_D4,
    8, PIT_D4, 8,
    // 8
    PIT_D4, 8, PIT_A4, 8, PIT_A4, 8, PIT_GS4, 8, PIT_G4, 8, PIT_NONE, 4,
    // 9
    PIT_A4, 8, PIT_A4, 8, PIT_A4, 8, PIT_B4, 8, PIT_C5, 8, PIT_C5, 8, PIT_C5, 4,
    // 10
    PIT_B4, 8, PIT_B4, 8, PIT_B4, 8, PIT_B4, 8, PIT_A4, 4, PIT_NONE, 4,
    // 11
    PIT_NONE, 8, PIT_G4, 8, PIT_G4, 8, PIT_GS4, 8, PIT_A4, 8, PIT_A4, 8, PIT_A4,
    8, PIT_GS4, 8,
    // 12
    PIT_G4, 4, PIT_B4, 4, PIT_C5, 4, PIT_NONE, 4,
    // 13
    PIT_C4, 8, PIT_C4, 8, PIT_C4, 8, PIT_E4, 8, PIT_A4, 8, PIT_A4, 8, PIT_A4, 8,
    PIT_NONE, 8,
    // 14
    PIT_D4, 8, PIT_D4, 8, PIT_D4, 8, PIT_F4, 8, PIT_G4, 8, PIT_G4, 8, PIT_G4, 8,
    PIT_NONE, 8,
    // 15
    PIT_NONE, 8, PIT_G4, 8, PIT_G4, 8, PIT_GS4, 8, PIT_A4, 8, PIT_A4, 8, PIT_A4,
    8, PIT_GS4, 8,
    // 16
    PIT_G4, 4, PIT_B4, 4, PIT_C5, 4, PIT_NONE, 4,
    // 終端データ
    0, 0};

uint16_t bgm_1_b[] = {
    // 1
    PIT_C3, 4, PIT_C3, 4, PIT_A3, 4, PIT_A3, 4,
    // 2
    PIT_D3, 4, PIT_D3, 4, PIT_G3, 4, PIT_G3, 4,
    // 3
    PIT_G3, 4, PIT_G3, 4, PIT_G3, 4, PIT_G3, 4,
    // 4
    PIT_G3, 4, PIT_D3, 4, PIT_C3, 4, PIT_NONE, 4,
    // 5
    PIT_C3, 2, PIT_C3, 2,
    // 6
    PIT_C3, 2, PIT_C3, 2,
    // 7
    PIT_D3, 2, PIT_D3, 2,
    // 8
    PIT_D3, 2, PIT_G3, 2,
    // 9
    PIT_F3, 2, PIT_F3, 2,
    // 10
    PIT_E3, 2, PIT_A3, 2,
    // 11
    PIT_G3, 2, PIT_G3, 2,
    // 12
    PIT_G3, 4, PIT_D3, 4, PIT_C3, 4, PIT_NONE, 4,
    // 13
    PIT_C3, 4, PIT_C3, 4, PIT_A3, 4, PIT_A3, 4,
    // 14
    PIT_D3, 4, PIT_D3, 4, PIT_G3, 4, PIT_G3, 4,
    // 15
    PIT_G3, 4, PIT_G3, 4, PIT_G3, 4, PIT_G3, 4,
    // 16
    PIT_G3, 4, PIT_D3, 4, PIT_C3, 4, PIT_NONE, 4,
    // 終端データ
    0, 0};

uint16_t* p_bgm_1[2] = {bgm_1_a, bgm_1_b};

// se
uint16_t se_1[] = {PIT_C5, 32, PIT_D5, 32, PIT_E5, 32, PIT_F5, 32, PIT_G5, 32,
                   PIT_A5, 32, PIT_B5, 32,
                   // 終端データ
                   0, 0};
                   
uint16_t* p_se_1 = se_1;

notes.h

#ifndef MUSIC_DATA_H
#define MUSIC_DATA_H

#include "pitches.h"
#include "stdint.h"

// 音符 構造体
typedef struct {
  uint16_t pitch;      // 周波数(音程)
  uint8_t note_value;  // 音符種類 (1: 全音符, 2: 2分音符, 4: 4分音符, ...)
} Note;

extern uint16_t* p_bgm_1[2];
extern uint16_t* p_se_1;
#endif  // MUSIC_DATA_H

pitches.h

#define PIT_NONE 0
// #define PIT_B0  31
// #define PIT_C1  33
// #define PIT_CS1 35
// #define PIT_D1  37
// #define PIT_DS1 39
// #define PIT_E1  41
// #define PIT_F1  44
// #define PIT_FS1 46
// #define PIT_G1  49
// #define PIT_GS1 52
// #define PIT_A1  55
// #define PIT_AS1 58
// #define PIT_B1  62
// #define PIT_C2  65
// #define PIT_CS2 69
// #define PIT_D2  73
// #define PIT_DS2 78
// #define PIT_E2  82
// #define PIT_F2  87
// #define PIT_FS2 93
// #define PIT_G2  98
// #define PIT_GS2 104
// #define PIT_A2  110
// #define PIT_AS2 117
// #define PIT_B2  123
#define PIT_C3 131
#define PIT_CS3 139
#define PIT_D3 147
#define PIT_DS3 156
#define PIT_E3 165
#define PIT_F3 175
#define PIT_FS3 185
#define PIT_G3 196
#define PIT_GS3 208
#define PIT_A3 220
#define PIT_AS3 233
#define PIT_B3 247
#define PIT_C4 262
#define PIT_CS4 277
#define PIT_D4 294
#define PIT_DS4 311
#define PIT_E4 330
#define PIT_F4 349
#define PIT_FS4 370
#define PIT_G4 392
#define PIT_GS4 415
#define PIT_A4 440
#define PIT_AS4 466
#define PIT_B4 494
#define PIT_C5 523
#define PIT_CS5 554
#define PIT_D5 587
#define PIT_DS5 622
#define PIT_E5 659
#define PIT_F5 698
#define PIT_FS5 740
#define PIT_G5 784
#define PIT_GS5 831
#define PIT_A5 880
#define PIT_AS5 932
#define PIT_B5 988
// #define PIT_C6  1047
// #define PIT_CS6 1109
// #define PIT_D6  1175
// #define PIT_DS6 1245
// #define PIT_E6  1319
// #define PIT_F6  1397
// #define PIT_FS6 1480
// #define PIT_G6  1568
// #define PIT_GS6 1661
// #define PIT_A6  1760
// #define PIT_AS6 1865
// #define PIT_B6  1976
// #define PIT_C7  2093
// #define PIT_CS7 2217
// #define PIT_D7  2349
// #define PIT_DS7 2489
// #define PIT_E7  2637
// #define PIT_F7  2794
// #define PIT_FS7 2960
// #define PIT_G7  3136
// #define PIT_GS7 3322
// #define PIT_A7  3520
// #define PIT_AS7 3729
// #define PIT_B7  3951
// #define PIT_C8  4186
// #define PIT_CS8 4435
// #define PIT_D8  4699
// #define PIT_DS8 4978

psg.c

#include "psg.h"

#include <stdio.h>

uint8_t psg_regs[][3] = {{REG_CH_A_LOW, REG_CH_A_HIGH, REG_CH_A_VOLUME},
                         {REG_CH_B_LOW, REG_CH_B_HIGH, REG_CH_B_VOLUME},
                         {REG_CH_C_LOW, REG_CH_C_HIGH, REG_CH_C_VOLUME}};
uint8_t is_interrupt = 0;

uint16_t* notes[3];
uint16_t* notes_copy[3];
uint32_t base_duration[3];
uint16_t note_duration[3];
uint8_t is_done[3];

int8_t bgm_repeat;  // -1: 無限繰り返し, 0: 繰り返し0回, 1: 繰り返し1回, ...
int8_t se_repeat;
uint8_t is_bgm_enable = 0;
uint8_t is_se_enable = 0;
uint8_t bgm_id;
uint8_t se_id;
void (*bgm_callback)(uint8_t id);
void (*se_callback)(uint8_t id);

void play_bgm(uint16_t* pointer[2], uint16_t bpm, uint8_t volume,
              uint8_t repeat, uint16_t id, void (*callback)(uint8_t id)) {
  is_bgm_enable = 0;

  bpm = bpm > 0 ? bpm : BASE_BPM;
  for (uint8_t ch = 0; ch < 2; ch++) {
    notes[ch] = pointer[ch];
    notes_copy[ch] = pointer[ch];
    base_duration[ch] = BASE_DURATION * BASE_BPM / bpm;
    note_duration[ch] = 0;
    set_volume(ch, volume);
    is_done[ch] = 0;
  }
  bgm_repeat = repeat;
  bgm_id = id;
  bgm_callback = callback;

  if (!is_interrupt) {
    start_interrupt();
  }
  is_bgm_enable = 1;
}

void stop_bgm() {
  bgm_repeat = 0;
  is_bgm_enable = 0;
  for (uint8_t ch = 0; ch < 2; ch++) {
    set_pitch(ch, PIT_NONE);
    note_duration[ch] = 0;
    is_done[ch] = 1;
  }
}

void play_se(uint16_t* pointer, uint16_t bpm, uint8_t volume, uint8_t repeat,
             uint16_t id, void (*callback)(uint8_t id)) {
  is_se_enable = 0;

  bpm = bpm > 0 ? bpm : BASE_BPM;
  notes[CHANNEL_C] = pointer;
  notes_copy[CHANNEL_C] = pointer;
  base_duration[CHANNEL_C] = BASE_DURATION * BASE_BPM / bpm;
  note_duration[CHANNEL_C] = 0;
  set_volume(CHANNEL_C, volume);
  is_done[CHANNEL_C] = 0;

  se_repeat = repeat;
  se_id = id;
  se_callback = callback;

  if (!is_interrupt) {
    start_interrupt();
  }
  is_se_enable = 1;
}

void stop_se() {
  se_repeat = 0;
  is_se_enable = 0;
  set_pitch(CHANNEL_C, PIT_NONE);
  note_duration[CHANNEL_C] = 0;
  is_done[CHANNEL_C] = 1;
}

// 音符設定
void set_note() {
  for (uint8_t ch = 0; ch < 3; ch++) {
    if (is_done[ch]) {
      continue;
    }

    if (!is_bgm_enable && ch < CHANNEL_C) {
      continue;
    }

    if (!is_se_enable && ch == CHANNEL_C) {
      continue;
    }

    if (note_duration[ch] > 0) {
      note_duration[ch]--;
      continue;
    }

    // 音程
    uint16_t pitch = *notes[ch];
    set_pitch(ch, pitch);

    // 音符の長さ
    uint8_t note_value = *(notes[ch] + 1);
    note_duration[ch] = note_value > 0 ? (base_duration[ch] / note_value) : 0;

    if (pitch == 0 && note_value == 0) {
      is_done[ch] = 1;
    } else {
      notes[ch] += 2;
    }
  }

  check_loop();
}

void check_loop() {
  // bgm
  uint8_t bgm_done = is_done[CHANNEL_A] && is_done[CHANNEL_B];
  if (is_bgm_enable && bgm_done) {
    if (bgm_repeat == 0) {
      is_bgm_enable = 0;
      if (bgm_callback != NULL) {
        // コールバック実行
        bgm_callback(bgm_id);
      }
    } else {
      if (bgm_repeat > 0) {
        // 繰り返し
        bgm_repeat--;
      }

      for (uint8_t ch = 0; ch < 2; ch++) {
        notes[ch] = notes_copy[ch];
        note_duration[ch] = 0;
        is_done[ch] = 0;
      }
    }
  }

  // se
  uint8_t se_done = is_done[CHANNEL_C];
  if (is_se_enable && se_done) {
    if (se_repeat == 0) {
      is_se_enable = 0;
      if (se_callback != NULL) {
        // コールバック実行
        se_callback(se_id);
      }
    } else {
      // 繰り返し
      if (se_repeat > 0) {
        se_repeat--;
      }

      notes[CHANNEL_C] = notes_copy[CHANNEL_C];
      note_duration[CHANNEL_C] = 0;
      is_done[CHANNEL_C] = 0;
    }
  }

  if (!is_bgm_enable && !is_se_enable) {
    stop_interrupt();
  }
}

void set_pitch(uint8_t channel, uint16_t pitch) {
  // PSGに周波数設定 クロック 1.789773 MHz
  unsigned int n = pitch > 0 ? (1789773 / (16 * pitch)) : 0;

  // チャンネルA
  __outp(PORT_PSG_REG, psg_regs[channel][0]);  // 下位8ビット
  __outp(PORT_PSG_DATA, n & 0xFF);
  __outp(PORT_PSG_REG, psg_regs[channel][1]);  // 上位4ビット
  __outp(PORT_PSG_DATA, (n >> 8) & 0x0F);
}

// 音量設定
void set_volume(uint8_t channel, uint8_t volume) {
  __outp(PORT_PSG_REG, psg_regs[channel][2]);  // ボリューム
  __outp(PORT_PSG_DATA, volume);
}

// 割り込みが発生したときに実行する関数のアドレスを設定
void start_interrupt() {
  is_interrupt = 1;

  uint16_t addr = set_note;  // この関数を定期的に実行する
  __asm__("di");             // 割り込み無効
  volatile unsigned char* vec =
      (volatile unsigned char*)WORK_H_TIMI;      // フック アドレス
  vec[0] = 0xC3;                                 // JP命令
  vec[1] = (unsigned char)(addr & 0xFF);         // 下位アドレス
  vec[2] = (unsigned char)((addr >> 8) & 0xFF);  // 上位アドレス
  __asm__("ei");
}

void stop_interrupt() {
  __asm__("di");  // 割り込み無効
  volatile unsigned char* vec =
      (volatile unsigned char*)WORK_H_TIMI;  // フック アドレス
  vec[0] = 0xC9;                             // RET命令
  vec[1] = 0xC9;
  vec[2] = 0xC9;
  __asm__("ei");  // 割り込み有効化

  is_interrupt = 0;
}

psg.h

#ifndef PSG_H
#define PSG_H

#include <stdint.h>

#include "pitches.h"

#define PORT_PSG_REG 0xA0   // PSGポート
#define PORT_PSG_DATA 0xA1  // PSGポート

#define REG_CH_A_LOW 0      // チャンネルA 音程分周比 下位8ビット レジスタ番号
#define REG_CH_A_HIGH 1     // チャンネルA 音程分周比 上位4ビット レジスタ番号
#define REG_CH_B_LOW 2      // チャンネルB 音程分周比 下位8ビット レジスタ番号
#define REG_CH_B_HIGH 3     // チャンネルB 音程分周比 上位4ビット レジスタ番号
#define REG_CH_C_LOW 4      // チャンネルC 音程分周比 下位8ビット レジスタ番号
#define REG_CH_C_HIGH 5     // チャンネルC 音程分周比 上位4ビット レジスタ番号
#define REG_CH_A_VOLUME 8   // チャンネルA ボリューム
#define REG_CH_B_VOLUME 9   // チャンネルB ボリューム
#define REG_CH_C_VOLUME 10  // チャンネルC ボリューム

#define WORK_H_TIMI 0xFD9F  // フック アドレス

#define BASE_BPM 120
#define BASE_DURATION 120  // 全音符の長さ

#define CHANNEL_A 0
#define CHANNEL_B 1
#define CHANNEL_C 2

void play_bgm(uint16_t* pointer[2], uint16_t bpm, uint8_t volume,
              uint8_t repeat, uint16_t id, void (*callback)(uint8_t id));
void stop_bgm();
void play_se(uint16_t* pointer, uint16_t bpm, uint8_t volume, uint8_t repeat,
             uint16_t id, void (*callback)(uint8_t id));
void stop_se();
void start_interrupt();
void stop_interrupt();
void set_note();
void set_pitch(uint8_t channel, uint16_t pitch);
void set_volume(uint8_t channel, uint8_t volume);
void check_loop();
#endif

.vscode/c_cpp_properties.json

{
    "configurations": [
        {
            "name": "z88dk-msx",
            "includePath": [
                "${workspaceFolder}/**",
                "C:/z88dk/include"
            ],
            "defines": [],
            "compilerPath": "C:/z88dk/bin/zcc.exe",
            "cStandard": "c89",
            "intelliSenseMode": "${default}"
        }
    ],
    "version": 4
}

.vscode/launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Run MSX ROM in Emulator",
            "type": "cppdbg",
            "request": "launch",
            "program": "C:/openmsx-21.0-windows-vc-x64-bin/openmsx.exe",
            "args": [
                "${workspaceFolder}/${fileBasenameNoExtension}.rom"
            ],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "externalConsole": false,
            "MIMode": "gdb",
            "miDebuggerPath": "",
            "preLaunchTask": "Build MSX ROM"
        }
    ]
}

.vscode/tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Build MSX ROM",
            "type": "shell",
            "command": "mingw32-make",
            "args": [
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "problemMatcher": []
        },
        {
            "label": "make clean",
            "type": "shell",
            "command": "mingw32-make",
            "args": [
                "clean"
            ],
        }
    ]
}