Multiple Pushbuttons with Toggle

I coded a simple synth where

Pitch = sensor value * 2

But then I gave it a shot to make it more interesting.

I want to have 4 toggle-able pushbuttons which replace the "multiplier" with a variable multiplier.

This way, depending on what button was pressed last, the pitch is unique from the others.

I sort of left the coding at a cliffhanger. Any help or advice at all really is appreciated.

//declare variables:
const int b1Pin = 3;
const int b2Pin = 4;
const int b3Pin = 5;
const int b4Pin = 6;
int varPin = analogRead(A0);
int button1 = digitalRead(b1Pin);
int button2 = digitalRead(b2Pin); 
int button3 = digitalRead(b3Pin); 
int button4 = digitalRead(b4Pin); 
int lastButtonPressed = 1;
int currentButton = 1;
int buttonState = 0;
int lastButtonState = 0;

void setup(){}  

void loop()
{

  //Button input changes variable currentButton
  if (button1 == HIGH)
  {currentButton == 1;}
  if (button2 == HIGH)
  {currentButton == 2;}
  if (button3 == HIGH)
  {currentButton == 3;}
  if (button4 == HIGH)
  {currentButton == 4;}
  if (currentButton != lastButtonPressed) //If new button isn't the same as last
  {lastButtonPressed = currentButton;}    //Change it to new value
  
  int varPitch = map(varPin, 100, 1000, 100, 5000) * lastButtonPressed;
  //Pitch will equal sensor value times the "button multiplier".
  tone(7, varPitch); //Play it. 
}

I havent scanned the whole thing but this did jump out at me:

if (button1 == HIGH) {currentButton == 1;}

should be: (one equals sign for assignment)

if (button1 == HIGH) {currentButton = 1;}

You have a few of them like that.

Yeah, I must've overlooked it.

Thanks for catching that.