int ledPin = 13;
int LDR  = 5;   // A5
int LDR2 = 0;   // A0
int val  = 0;
int val2 = 0;

const byte buzzPin  = 10;
const byte buzzPin2 = 12;

void playTones(int freq1, int freq2, int duration_ms) {
  long period1 = freq1 > 0 ? 1000000L / freq1 : 0;
  long period2 = freq2 > 0 ? 1000000L / freq2 : 0;
  long half1   = period1 / 2;
  long half2   = period2 / 2;

  long startTime = millis();
  long t1 = 0, t2 = 0;
  bool state1 = false, state2 = false;

  while (millis() - startTime < duration_ms) {
    long now = micros();

    if (freq1 > 0 && now - t1 >= half1) {
      state1 = !state1;
      digitalWrite(buzzPin, state1);
      t1 = now;
    }

    if (freq2 > 0 && now - t2 >= half2) {
      state2 = !state2;
      digitalWrite(buzzPin2, state2);
      t2 = now;
    }
  }

  digitalWrite(buzzPin,  LOW);
  digitalWrite(buzzPin2, LOW);
}

void setup() {
  pinMode(ledPin,   OUTPUT);
  pinMode(buzzPin,  OUTPUT);
  pinMode(buzzPin2, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  val  = analogRead(LDR);
  val2 = analogRead(LDR2);

  Serial.print("LDR1: ");
  Serial.print(val);
  Serial.print(" | LDR2: ");
  Serial.println(val2);

  int freq1 = map(val,  0, 1023, 200, 2000);
  int freq2 = map(val2, 0, 1023, 200, 2000);

  // оба буззера играют одновременно 100мс
  playTones(freq1, freq2, 100);

  if (val < 512) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
}