Control sound using bluetooth

/*Bluetooth buzzer
 * Created on 2 febraury,2021
 * by zayed alam
 * Hi guys,
 * I am gonna show you how to control sounds using android app.It is a very simple
 * and fun project.This works like this:Go to the google play store.Search for"
 * Smart Bluetooth" and there will be a bluetooth logo.Install it.Then turn on 
 * your bluetooth,Then click on "Search".After sometime after searching,you will
 * find "HC-05" and that is our bluetooth module.click on it.Then it will ask to 
 * Select a theme by holding on the any of the two options.Then after it has
 * conected,on the top right corner,there will be a settings sign.Click on it.
 * Then a drop down box shows.Then click on terminal.Then if you type 'a',you 
 * will hear a sound by the buzzer.That means it is working.You will figure 
 * something on my code like"if(data=='e'){"That means if you type 'e' key,
 * it will create a sound from the buzzer.You can also edit the keys or create
 * a new condition like if we type this key,it will make this sound.
 * 
 * That's all of that.For more stffs like schematics and what are the materials
 * you have to gather,go to:https://create.arduino.cc/projecthub/zayedalam/control-sound-using-bluetooth-a670ee
 */

char data = '5'; //Variable for storing received data  
const int buzzer=2;//Buzzers pin

void setup() {
  // put your setup code here, to run once:
    Serial.begin(9600); //Sets the baud for serial data transmission 
    pinMode(buzzer,OUTPUT);//defining the buzzer                    

}

void loop() {
  // put your main code here, to run repeatedly:
  if(Serial.available() > 0)  // Send data only when you receive data:  
   {  
      data = Serial.read();

       if(data=='a'){//If you will type 'a',
        tone(buzzer,1000);//make a sound
        delay(20);
        noTone(buzzer);
        
       }
       if (data=='b'){//If you will type 'b',
        tone(buzzer,100);//Make a sound
        delay(20);
        noTone(buzzer);
       }
if(data=='c'){//if you will type c
  tone(buzzer,90);//Make a sound
  delay(20);
  noTone(buzzer);
}
if (data=='d'){
  tone(buzzer,345);
  delay(20);
  noTone(buzzer);
}
if(data=='e'){
  tone(buzzer,10);
  delay(20);
  noTone(buzzer);
}
   }
}