Jeep LED bars vu meter

Hi
can anyone see the code if i did it right?
its working but i am a beginner and maybe it can be done better.

this was a fun project, it was the first that i made.
first i wanted to get it to work by getting the data from speaker wire, it was working on the headphone jack on the pc but on the jeep i damaged my arduino.... yes after that i found out that there is -v and +v.....
so i went with a small sound sensor that i got in a kit. unsoldered the microphone and extended to place it close to the sub woofer and the electronic stuff in front of the jeep.
what i did is it takes 50 readings and take the highest one and use that to see what relay have to be on or off.

here is the code and i can not uploaded a mp4 file off the jeep with the working vu meter led bars
tomorrow i will upload a video to youtube and post a link

int maxval = 0;
uint32_t lastSample = 0;
int led1 = 5;
int led2 = 6;
int led3 = 7;
int led4 = 8;

void setup() {
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);

digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH);
Serial.begin(9600);
}

void loop() {
if (millis() - lastSample > 50) { // Every 100ms:
lastSample = millis();
Serial.println(maxval);
maxval = 0;
}
int reading = analogRead(0);
if (reading > maxval) {
maxval = reading;
}

if (maxval > 775) {
digitalWrite(led1, LOW);
delay(0);
}
if (maxval < 775) {
digitalWrite(led1, HIGH);
}
if (maxval > 790) {
digitalWrite(led2, LOW);
delay(0);
}
if (maxval < 790) {
digitalWrite(led2, HIGH);
}
if (maxval > 810) {
digitalWrite(led3, LOW);
delay(0);
}
if (maxval < 810) {
digitalWrite(led3, HIGH);
}
if (maxval > 850) {
digitalWrite(led4, LOW);
delay(0);
}
if (maxval < 850) {
digitalWrite(led4, HIGH);

}
delay(1);
}

One improvement would be to get rid of these:

delay(0);

Also, any time you find yourself using variables called led1, led2, led3, it's a strong hint that you should look at arrays.