SOLVED! Is there an easier way to alter this to oscillate an output?

// give it a name:
int x;
int led4 = 4;   //light
int led3 = 3;   //n/c
int led6 = 6;   //n/c
int led5 = 5;   //buzzer
int led13 = 13;   //n/c
int state10 = 1;
int state11 = 1;
int state12 = 1;
//          on    off   on   off  on  off on off  on  off   on  off   on off  on off  on off  on off  on off
int t1[] = {15000,14500,500,12000,500,500,500,500,500,15000,500,12000,500,500,500,500,500,500,500,500,500,500};
//           0     1     2   3    4   5   6   7    8   9    10   11   12  13  14  15  16  17  18  19  20  21

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  pinMode(led3, OUTPUT); 
  pinMode(led4, OUTPUT);  //buzzer
  pinMode(led5, OUTPUT);   //light
  pinMode(led6, OUTPUT);
  pinMode(led13, OUTPUT);
  pinMode(10,INPUT_PULLUP);
  pinMode(11,INPUT_PULLUP);
  pinMode(12,INPUT_PULLUP);
Serial.begin (115200);  
}
// the loop routine runs over and over again forever:
void loop(){
  state11 = digitalRead(11);
  state12 = digitalRead(12);
          Serial.println (state11);
          Serial.println (state12);
  if(state12==LOW)
    {
    for (x=0;x<22;x=x+1)
      {//9 different array variables +1 for array (0-9)

        Serial.println (x);
        Serial.println (t1[x]);
        if (x==1 || x==3 || x==5 || x==7 || x==9 || x==11 || x==13 || x==15 || x==17 || x==19)
          {   
          digitalWrite(led5, HIGH);   // turn the LED on (HIGH is the voltage level)
          digitalWrite(led4, HIGH);   // turn the LED on (HIGH is the voltage level)
          }
        if (x==0 || x==2 || x==4 || x==6 || x==8 || x==10 || x==12 || x==14 || x==16 || x==18 ||x==20 ||x==21)
          { 
          digitalWrite(led5, LOW);    // turn the LED off by making the voltage LOW
          digitalWrite(led4, LOW);    // turn the LED off by making the voltage LOW
          }
          if (x==0)
          {
            delay (250);
            digitalWrite(led4, HIGH);   // turn the LED on (HIGH is the voltage level)
          }
           if (x==1)
          {
            digitalWrite(led4, LOW);   // turn the LED off by making the voltage LOW
            delay (250);
            digitalWrite(led4, HIGH);   // turn the LED on (HIGH is the voltage level)
          }
        delay(t1[x]);             // wait for period t1(x)
      }
    }
   if (state12==HIGH)
    {
    digitalWrite(led4
    , HIGH);
    digitalWrite(led5, HIGH);
    } 
  state10 = digitalRead(10);
  if (state10 == LOW)
    {
    digitalWrite(led5, LOW);   // turn the LED on (HIGH is the voltage level)
    digitalWrite(led4, LOW);   // turn the LED on (HIGH is the voltage level)
    delay (500);
    digitalWrite(led4, HIGH);
    digitalWrite(led5, HIGH);
    delay (30000);
    }
}

The code is for a timer that runs through a series of sequences putting a light and a buzzer on at preset times.
I now need the buzzer to oscillate instead of just switch on and off, as the new buzzer only works this way, the old one just needed a voltage. (D5 in the sketch)
Is there any way to do this without totally altering everything to include millis instead of delays?
Thanks.

You could use the tone library.

But uhm

// give it a name:

WHY on earth don’t you!? ‘led4’ is as useful as just 4 or as useful as ‘monkey’.

Having said that, are you certain its a buzzer and not a piezo speaker? Some of them look remakably similar.

DKWatson:
Having said that, are you certain its a buzzer and not a piezo speaker? Some of them look remakably similar.

Yes I think the old one was a buzzer and the new one is a piezo speaker that needs an oscillating signal.

You might try:

tone(led5,440);   // buzzer ON, 440 Hz is note "A", adjust to suit
noTone(led5);     //   "    OFF

https://www.arduino.cc/reference/en/language/functions/advanced-io/tone/

Thank you outsider that is exactly what I wanted.