int conductor_beat = 0;

void wait_for_beat(int current_beat);
void release_beat();

// This is ABC notation;
const char *Canon_in_D[4][8] = {
    {"D4", "A3", "B3", "F#3", "G3", "D3", "G3", "A3"},

    // Below lines are generated by deepseek-r1
    {"A3", "E3", "F#3", "C#3", "D3", "A2", "D3", "E3"},
    {"F#3", "C#3", "D3", "A3", "B2", "F#2", "B2", "C#3"},
    {"D3", "A2", "B2", "F#2", "G2", "D2", "G2", "A2"},
};

void T_player(int id) {
    for (int i = 0; i < LENGTH(Canon_in_D[0]); i++) {
        wait_for_beat(i);
        const char *note = Canon_in_D[id - 1][i];

        // This is also UNIX philosophy: make everything
        // work together!
        char cmd[128];
        sprintf(cmd,
            "ffplay -nodisp -autoexit"
            " -loglevel quiet"
            " notes/%s.wav"
            " > /dev/null &", note);

        // Should not use "system" like this
        // in production code.
        system(cmd);
    }
}

void T_conductor() {
    // This conductor is not full synchronized with the players.
    // You may make the system out of sync.

    char buf[32];
    while (1) {
        printf("(conductor) > ");
        if (!fgets(buf, sizeof(buf), stdin)) {
            exit(0);
        }
        release_beat();
    }
}

int main() {
    for (int i = 0; i < LENGTH(Canon_in_D); i++) {
        spawn(T_player);
    }
    spawn(T_conductor);
}