int ereaseRow = 0;
boolean doErease = false;

void setBeat(int index, int sample) {
   samples[sample][index] = true;
}

void keyPressed() {
  println(keyCode);
  if(keyCode >= 48 && keyCode < 53) {
    ereaseRow = keyCode-48;
  } else if(keyCode >= 74) {
    if(key == 'p') {
      controller[0] = controller[0] == "PLAY" ? "STOP" : "PLAY";
      beat=0;
    }
  } else {
    int sample = keyCode-65;
    doErease = ereaseRow>0;
    if(sample >= 0 && sample < numSounds && !doErease) {
      setBeat(beat, sample);
    }
  }
}