Arduino - code - Happy Birthday Melody with flickering candle

/*  Happy Birthday Melody with flickering Candle
 *  By Chris Hawkins  November 2009
 *  with modified code from the  Melody example
 * (cleft) 2005 D. Cuartielles for K3
 *
 *
 * Taken from (cleft) 2005 D. Cuartielles for K3
 *
 * The calculation of the tones is made following the mathematical
 * operation:
 *
 *       timeHigh = period / 2 = 1 / (2 * toneFrequency)
 *
 * where the different tones are described as in the table:
 *
 * note  frequency  period  timeHigh
 * c 1         261 Hz          3830  1915  
 * d 2         294 Hz          3400  1700  
 * e 3         329 Hz          3038  1519  
 * f 4         349 Hz          2864  1432  
 * g 5         392 Hz          2550  1275  
 * a 6         440 Hz          2272  1136  
 * b 7         493 Hz          2028 1014 
 * C 8         523 Hz         1912  956
 *
 * http://www.arduino.cc/en/Tutorial/Melody
 *
 *
 */ 
int speaker = 6;
int led1pin = 9; // RED LED
int led2pin = 10; // Yellow LED
int button =4; // state swicth to play music
int x = 0;
int buttonState = 0;
int length = 28; // the number of notes
char notes[] = "ccdcfe ccdcgf ccCafed bbafgf"; // a space represents a rest
int beats[] = { 1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1, 1,1,1,1,1,1,1,1,1,1,1,1,2};
int tempo = 300; 
void playTone(int tone, int duration) {
  for (long i = 0; i < duration * 1000L; i += tone * 2) {
    digitalWrite(speaker, HIGH);
    delayMicroseconds(tone);
    digitalWrite(speaker, LOW);
    delayMicroseconds(tone);
  }
} 
void playNote(char note, int duration) {
  char names[] = {
    'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C'   };
  int tones[] = {
    1915, 1700, 1519, 1432, 1275, 1136, 1014, 956   }; 
  // play the tone corresponding to the note name
  for (int i = 0; i < 8; i++) {
    if (names[i] == note) {
      playTone(tones[i], duration);
    }
  }
} 
void playmusic ()
{
  for (int i = 0; i < length; i++) {
    if (notes[i] == ' ') {
      delay(beats[i] * tempo); // rest
    }
    else {
      if (i % 2 == 0)
      {
        analogWrite (led1pin,200);
       analogWrite (led2pin,100);
      }
      else {
        analogWrite (led1pin,100);
        analogWrite (led2pin,200);
      }
      playNote(notes[i], beats[i] * tempo);
     
    } 
    // pause between notes
    delay(tempo / 2);
  }
  digitalWrite (led1pin,LOW);
  digitalWrite (led2pin,LOW);
} 
void setup() {
  pinMode(speaker, OUTPUT); /* Speaker to play tune */
  pinMode(led1pin, OUTPUT); /* Red led from tri colour LED */
  pinMode(led2pin, OUTPUT); /* Yellow led from tri colour LED */
  pinMode (button, INPUT);  /* Start playing melody button */
} 
void loop(){
  buttonState = digitalRead (button); /* check if button pressed */
  if (buttonState == HIGH){
    playmusic();
  }
}