Never gonna Give you Up With Passive Buzzer!

/*  RickRollCode

    AUTHOR: Rowan Packard
    rowanpackard@gmail.com

    DISCLAIMER: The song "Never Gonna Give You Up" by Rick Astley
    is not the creative property of the author. This code simply
    plays a Piezo buzzer rendition of the song.
*/

#define  a3f    208     // 208 Hz
#define  b3f    233     // 233 Hz
#define  b3     247     // 247 Hz
#define  c4     261     // 261 Hz MIDDLE C
#define  c4s    277     // 277 Hz
#define  e4f    311     // 311 Hz    
#define  f4     349     // 349 Hz 
#define  a4f    415     // 415 Hz  
#define  b4f    466     // 466 Hz 
#define  b4     493     // 493 Hz 
#define  c5     523     // 523 Hz 
#define  c5s    554     // 554 Hz
#define  e5f    622     // 622 Hz  
#define  f5     698     // 698 Hz 
#define  f5s    740     // 740 Hz
#define  a5f    831     // 831 Hz 

#define rest    -1

int piezo = 9; // Connect your piezo buzzer to this pin or change it to match your circuit!
int led = LED_BUILTIN; 

volatile int beatlength = 100; // determines tempo
float beatseparationconstant = 0.3;

int threshold;

int a; // part index
int b; // song index
int c; // lyric index

boolean flag;

// Parts 1 and 2 (Intro)

int song1_intro_melody[] =
{c5s, e5f, e5f, f5, a5f, f5s, f5, e5f, c5s, e5f, rest, a4f, a4f};

int song1_intro_rhythmn[] =
{6, 10, 6, 6, 1, 1, 1, 1, 6, 10, 4, 2, 10};

// Parts 3 or 5 (Verse 1)

int song1_verse1_melody[] =
{ rest, c4s, c4s, c4s, c4s, e4f, rest, c4, b3f, a3f,
  rest, b3f, b3f, c4, c4s, a3f, a4f, a4f, e4f,
  rest, b3f, b3f, c4, c4s, b3f, c4s, e4f, rest, c4, b3f, b3f, a3f,
  rest, b3f, b3f, c4, c4s, a3f, a3f, e4f, e4f, e4f, f4, e4f,
  c4s, e4f, f4, c4s, e4f, e4f, e4f, f4, e4f, a3f,
  rest, b3f, c4, c4s, a3f, rest, e4f, f4, e4f
};

int song1_verse1_rhythmn[] =
{ 2, 1, 1, 1, 1, 2, 1, 1, 1, 5,
  1, 1, 1, 1, 3, 1, 2, 1, 5,
  1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3,
  1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 4,
  5, 1, 1, 1, 1, 1, 1, 1, 2, 2,
  2, 1, 1, 1, 3, 1, 1, 1, 3
};

const char* lyrics_verse1[] =
{ "We're ", "no ", "strangers ", "", "to ", "love ", "", "\r\n",
  "You ", "know ", "the ", "rules ", "and ", "so ", "do ", "I\r\n",
  "A ", "full ", "commitment's ", "", "", "what ", "I'm ", "thinking ", "", "of", "\r\n",
  "You ", "wouldn't ", "", "get ", "this ", "from ", "any ", "", "other ", "", "guy\r\n",
  "I ", "just ", "wanna ", "", "tell ", "you ", "how ", "I'm ", "feeling", "\r\n",
  "Gotta ", "", "make ", "you ", "understand", "", "\r\n"
};

// Parts 4 or 6 (Chorus)

int song1_chorus_melody[] =
{ b4f, b4f, a4f, a4f,
  f5, f5, e5f, b4f, b4f, a4f, a4f, e5f, e5f, c5s, c5, b4f,
  c5s, c5s, c5s, c5s,
  c5s, e5f, c5, b4f, a4f, a4f, a4f, e5f, c5s,
  b4f, b4f, a4f, a4f,
  f5, f5, e5f, b4f, b4f, a4f, a4f, a5f, c5, c5s, c5, b4f,
  c5s, c5s, c5s, c5s,
  c5s, e5f, c5, b4f, a4f, rest, a4f, e5f, c5s, rest
};

int song1_chorus_rhythmn[] =
{ 1, 1, 1, 1,
  3, 3, 6, 1, 1, 1, 1, 3, 3, 3, 1, 2,
  1, 1, 1, 1,
  3, 3, 3, 1, 2, 2, 2, 4, 8,
  1, 1, 1, 1,
  3, 3, 6, 1, 1, 1, 1, 3, 3, 3, 1, 2,
  1, 1, 1, 1,
  3, 3, 3, 1, 2, 2, 2, 4, 8, 4
};

const char* lyrics_chorus[] =
{ "Never ", "", "gonna ", "", "give ", "you ", "up\r\n",
  "Never ", "", "gonna ", "", "let ", "you ", "down", "", "\r\n",
  "Never ", "", "gonna ", "", "run ", "around ", "", "", "", "and ", "desert ", "", "you\r\n",
  "Never ", "", "gonna ", "", "make ", "you ", "cry\r\n",
  "Never ", "", "gonna ", "", "say ", "goodbye ", "", "", "\r\n",
  "Never ", "", "gonna ", "", "tell ", "a ", "lie ", "", "", "and ", "hurt ", "you\r\n"
};

void setup()
{
  pinMode(piezo, OUTPUT);
  pinMode(led, OUTPUT);

  digitalWrite(led, LOW);
  Serial.begin(9600);
  flag = true;
  a = 4;
  b = 0;
  c = 0;
}

void loop()
{


  // play next step in song
  if (flag == true) {
    play();
  }
}

void play() {
  int notelength;
  if (a == 1 || a == 2) {
    // intro
    notelength = beatlength * song1_intro_rhythmn[b];
    if (song1_intro_melody[b] > 0) {
      digitalWrite(led, HIGH);
      tone(piezo, song1_intro_melody[b], notelength);
    }
    b++;
    if (b >= sizeof(song1_intro_melody) / sizeof(int)) {
      a++;
      b = 0;
      c = 0;
    }
  }
  else if (a == 3 || a == 5) {
    // verse
    notelength = beatlength * 2 * song1_verse1_rhythmn[b];
    if (song1_verse1_melody[b] > 0) {
      digitalWrite(led, HIGH);
      Serial.print(lyrics_verse1[c]);
      tone(piezo, song1_verse1_melody[b], notelength);
      c++;
    }
    b++;
    if (b >= sizeof(song1_verse1_melody) / sizeof(int)) {
      a++;
      b = 0;
      c = 0;
    }
  }
  else if (a == 4 || a == 6) {
    // chorus
    notelength = beatlength * song1_chorus_rhythmn[b];
    if (song1_chorus_melody[b] > 0) {
      digitalWrite(led, HIGH);
      Serial.print(lyrics_chorus[c]);
      tone(piezo, song1_chorus_melody[b], notelength);
      c++;
    }
    b++;
    if (b >= sizeof(song1_chorus_melody) / sizeof(int)) {
      Serial.println("");
      a++;
      b = 0;
      c = 0;
    }
  }
  delay(notelength);
  noTone(piezo);
  digitalWrite(led, LOW);
  delay(notelength * beatseparationconstant);
  if (a == 7) { // loop back around to beginning of song
    a = 1;
  }
}