How can apply two filters to an audio input?

H0Ff3

I want to have amplitude values from highpass filtered and from a lowpass filtered audio signal so i can work with both.

import processing.sound.*;

//i made two signal streams to give each filter its own audio signal (which is actually unnecessary i think)
//i did this just to be sure:
Amplitude ampHP;
Amplitude ampLP;
AudioIn inHP;
AudioIn inLP;
LowPass lP;
HighPass hP;
//an index getting increased each frame in draw() function for visual stuff:
int i = 0;
int[][] randArr = new int[3][3];
//variables for containing the volume level value:
int volHP; 
int volLP;

void setup(){
  size(800, 800);
  background(0);
  frameRate(30);
  
  //lowpass:
  ampLP = new Amplitude(this);
  inLP = new AudioIn(this, 0);
  lP = new LowPass(this);
  
  inLP.start();
  lP.process(inLP, 80);
  ampLP.input(inLP);
  lP.stop();
  
  //highpass:
  ampHP = new Amplitude(this);
  inHP = new AudioIn(this, 0);
  hP = new HighPass(this);
  
  inHP.start();
  hP.process(inHP, 500);
  ampHP.input(inHP);
  
}

void draw(){
  //getting the values from the filtered streams:
  volHP = int(ampHP.analyze()*500);
  volLP = int(ampLP.analyze()*500);
  println(volHP, volLP); //for debugging. it looks like nothing at all happens to the audio
  
  //fancy stuff happening below. but not important for my question..
  background(0);
  translate(height/2, height/2);
  noFill();
  stroke(255);
  
  for(int j = 0; j < 3; j++){
    for(int k = 0; k < 3; k++){
      randArr[j][k] = int(random(10, 500)) - 250;
    }
  }
  
  if(volLP >= 180){
    noFill();
    strokeWeight(random(2, 50));
    for(int j = 0; j < 5; j++){
      ellipse(sin(radians(i))*height/5 + randArr[0][0]*0.7, cos(radians(i))*height/5 + randArr[0][1]*0.7, randArr[0][2], randArr[0][2]);
    }
  }
  
  if(volHP >= 180){
    fill(255);  
  }
  strokeWeight(1);
  ellipse(0, 0, volHP, volLP);
  //sin(radians(i))*height/5
  i+=10;
  
}

H0Ff3

I actuallly just had the idea to simply use an fft and just use the values from the frequency bands i want.. but i am still wondering why my first idea is not working. i would be very thankful if someone could explain that to me