Clone Hero Drums

I'm currently making some Drums for the game Clone Hero, and the Dolphin Emulator.
My problem is that I can't activate 2 Piezos at the same time. They work fine when I activate them alone but not 2 at the same time. I have a Arduino Pro Micro and use this library.

I'm really new to this whole Arduino thing, so I currently don't understand a ton.

Anyway, thanks in Advance.

#include <Joystick.h>

const int drum1 = A0;
const int drum2 = A1;
const int drum3 = A2;
const int drum4 = A3;

const int threshold = 100;

int sensorReading = 0;

Joystick_ Joystick;

void setup() {

  // Initialize Joystick Library

// Last state of the button
int lastButtonState = 0;

void loop() {

  sensorReading = analogRead(drum1);

  if (sensorReading >= threshold)

  sensorReading = analogRead(drum2);

  if (sensorReading >= threshold)


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