int buzzerpin = 7;

void setup() {

  Serial.begin(9600);

  Serial.println("Type a, b, c, d, e");

  for (int thisPin = 2; thisPin < 7; thisPin++) {

    pinMode(thisPin, OUTPUT);
    pinMode (buzzerpin, OUTPUT);

  }
}

void loop() {

  // read the sensor

  if (Serial.available() > 0) {

    int inByte = Serial.read();

    switch(inByte) {

      case 'a':

       digitalWrite(2, HIGH);

       tone(buzzerpin, 50, 1000);
       delay (1000);

       break;

      case 'b':

       digitalWrite(3, HIGH);

       tone(buzzerpin, 100, 1000);
       delay (1000);

       break;

      case 'c':

       digitalWrite(4, HIGH);

       tone(buzzerpin, 150, 1000);
       delay (1000);

       break;

      case 'd':

       digitalWrite(5, HIGH);

       tone(buzzerpin, 200, 1000);
       delay (1000);

       break;

       case 'e':

       digitalWrite(6, HIGH);

       tone(buzzerpin, 250, 1000);
       delay (1000);

       break;

      default:

       // turn all the LEDs off:

       for (int thisPin = 2; thisPin < 7; thisPin++) {

         digitalWrite(thisPin, LOW);

      }

    }

  }
}