void loop() {

for (int i = 0; i < length; i++) {
  if (notes[i] == ' ') {
    delay(beats[i] * tempo);
digitalWrite(13, HIGH);
delay(50);
digitalWrite(12, HIGH);
delay(50);
digitalWrite(11, HIGH);
delay(50);
digitalWrite(10, HIGH);
delay(50);
digitalWrite(13, LOW);
delay(50);
digitalWrite(12, LOW);
delay(50);
digitalWrite(11, LOW);
delay(50);
digitalWrite(10, LOW);
delay(50);
  } else {
    playNote(notes[i], beats[i] * tempo);
  }
  delay(tempo / 2);
}
break;
}