Light Sensitive Theremin

const int ldrPin = A3;
const int buzzerPin = A1;

// variable declaration
int value;  // sensor value
int low;    // low sensor value calibration
int high;   // high sensor value calibration
// LED pin alert calibration
int led = 13;
 
void setup() 
    {
      pinMode (buzzerPin, OUTPUT);
      pinMode (led, OUTPUT);
      // turn LED on
      digitalWrite(led, HIGH);
      // calibration for the first 3 seconds after program runs
      while (millis() < 3000) 
            {
              // record the maximum sensor value
              value = analogRead(ldrPin);
              if (value > high) 
                 {
                   high = value;
                 }
              // record the minimum sensor value
              if (value < low) 
                 {
                   low = value;
                 }
            }
      // turn LED off
      digitalWrite (led, LOW);
    }
 
void loop() 
     {
       //read the input from A0 and store it in a variable
       value = light();
       // map the sensor values to a frequency range 50 Hz - 4000 Hz
       int pitch = map(value, low, high, 100, 4000);
       // play the tone for 20 ms on buzzer pin 8
       speaker(pitch, 20);
       // wait for a moment
       delay(10);
     }
     
//function to calculate potentiometer value
int light()
   {
    int val = analogRead(ldrPin);
    return val;
   }

void speaker(unsigned int frequency, unsigned long duration)
            {
              tone(buzzerPin, frequency, duration);
            }