Star Wars "Imperial March" on Arduino

#include "pitches.h"

const int ledPin = 13;      // build-in LED
const int btnPin = 2;       // button pin
const int spkPin = 12;      // piezo speaker pin
const int ledPins[] { 5, 6, 7, 8, 9, 10 }; // "music visualization" LEDs

// Melody is written as:
// | note | duration | delay |
// note is predefined pitch value
// duration and delay are fractions of a second (1000 / N)
int melody[] = {
    // intro 1..
    NOTE_A3,    2,  8,
    NOTE_A3,    2,  8,
    NOTE_A3,    2,  8,
    NOTE_F3,    3,  8,
    NOTE_C4,    8,  16,
    NOTE_A3,    2,  8,
    NOTE_F3,    3,  8,
    NOTE_C4,    8,  16,
    NOTE_A3,    1,  8,
    // intro 2
    NOTE_E4,    2,  8,
    NOTE_E4,    2,  8,
    NOTE_E4,    2,  8,
    NOTE_F4,    3,  8,
    NOTE_C4,    8,  16,
    NOTE_GS3,   2,  8,
    NOTE_F3,    3,  8,
    NOTE_C4,    8,  16,
    NOTE_A3,    1,  8,

    // interesting part begins here :)
    NOTE_A4,    2,  8,
    NOTE_A3,    3,  8,
    NOTE_A3,    6,  16,
    NOTE_A4,    2,  8,
    NOTE_GS4,   4,  8,
    NOTE_G4,    4,  32,
    NOTE_FS4,   8,  32,
    NOTE_F4,    8,  32,
    NOTE_FS4,   4,  2,  // extra delay

    NOTE_AS3,   4,  8,
    NOTE_DS4,   2,  16,
    NOTE_D4,    4,  8,
    NOTE_CS4,   4,  32,
    NOTE_C4,    8,  32,
    NOTE_AS3,   8,  32,
    NOTE_C4,    4,  2,  // extra delay

    NOTE_F3,    8,  8,
    NOTE_GS3,   2,  16,
    NOTE_F3,    3,  32,
    NOTE_A3,    8,  16,
    NOTE_C4,    2,  16,
    NOTE_A4,    3,  32,
    NOTE_C4,    8,  32,
    NOTE_E4,    1,  8,

    // repeat...
    NOTE_A4,    2,  8,
    NOTE_A3,    3,  8,
    NOTE_A3,    6,  16,
    NOTE_A4,    2,  8,
    NOTE_GS4,   4,  8,
    NOTE_G4,    4,  32,
    NOTE_FS4,   8,  32,
    NOTE_F4,    8,  32,
    NOTE_FS4,   4,  2,  // extra delay

    NOTE_AS3,   4,  8,
    NOTE_DS4,   2,  16,
    NOTE_D4,    4,  8,
    NOTE_CS4,   4,  16,
    NOTE_C4,    8,  32,
    NOTE_AS3,   8,  32,
    NOTE_C4,    4,  2,  // extra delay

    NOTE_F3,    8,  8,
    NOTE_GS3,   2,  16,
    NOTE_F3,    3,  32,
    NOTE_C4,    8,  32,

    // ending
    NOTE_A3,    2,  8,
    NOTE_F3,    3,  8,
    NOTE_C3,    8,  16,
    NOTE_A3,    1,  1
};


int length = 66;
int noteIdx = 0;
int curDelay = 0;
unsigned long tmpTime = 0;

int ledState = LOW;
boolean pressed = false;

const int maxVal = 255;
int currentLedsAmount = 0;
int fadeInterval = 0;
int fadeTmp = 0;

void setLeds(int note)
{
    currentLedsAmount = map(note, NOTE_C3, NOTE_A4, 1, 3);
    updateLeds(currentLedsAmount);
}

void updateLeds(int amount)
{
    int vals[6] = {0,0,0,0,0,0};

    if (amount > 0) {
        vals[2] = maxVal;
        vals[3] = maxVal;
    }
    if (amount > 1) {
        vals[1] = maxVal;
                vals[4] = maxVal;
    }
    if (amount > 2) {
        vals[0] = maxVal;
        vals[5] = maxVal;
    }

    for (int i=0; i < 6; i++)
        analogWrite(ledPins[i], vals[i]);
}

void setup()
{
    pinMode(ledPin, OUTPUT);
    pinMode(spkPin, OUTPUT);
    pinMode(btnPin, INPUT);
    for (int i=0; i < 6; i++)
        pinMode(ledPins[i], OUTPUT);
    Serial.begin(9600);
}

void loop()
{
        // play next note
        unsigned long time = millis();
        unsigned long dt = time - tmpTime;
    if (ledState == HIGH)
    {
        if (dt > curDelay) {
            int freq = melody[noteIdx*3];
            int dur = 1000 / melody[noteIdx*3+1];
            curDelay = dur + 500 / melody[noteIdx*3+2];
            tmpTime = time;
                        fadeInterval = dur;
            setLeds(freq);
            tone(spkPin, freq, dur);
            if (++noteIdx >= length)
            noteIdx = 0;
        }
    }

    // check button state and set build-in LED

    int newState = digitalRead(btnPin);

    if (newState == HIGH && !pressed) {
                pressed = true;
    }
    else if (pressed && newState == LOW) {
            ledState = ledState == HIGH ? LOW : HIGH;
                noteIdx = 0;
            pressed = false;
    }

    digitalWrite(ledPin, ledState);

        dt = time - tmpTime;
        if (currentLedsAmount > 0 && dt > fadeInterval)
            updateLeds(0);
}