int ereaseRow = 0;
boolean doErease = false;
boolean doRec = false;

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

void keyPressed() {
  println(keyCode);
  if(keyCode >= 48 && keyCode < 57) { // From 0 to 9
    ereaseRow = keyCode-48;
  } else if(keyCode >= 74) { // From P to Z
    if(key == 'p') {
      controller[0] = controller[0] == "PLAY" ? "STOP" : "PLAY";
      beat=0;
    }
    if(key == 'r') {
      controller[1] = controller[1] == "UNSET" ? "REC/OVERDUB" : "UNSET";
      doRec = true;
    }
    if(key == 'x') {
      controller[1] = "EREASE";
    }
  } else { // From A to O
    int sample = keyCode-65;
    ereaseRow = controller[1] == "EREASE" ? keyCode-64 : 0;
    doErease = ereaseRow>0;
    if(sample >= 0 && sample < numSounds && !doErease) {
      if(controller[1] != "EREASE" && controller[1] != "UNSET") {
        setBeat(beat, sample);
      }
    }
  }
}