code: public void addIzouSoundLine(AddOnModel addOnModel, IzouSoundLineBaseClass izouSoundLine) {
          debug("adding soundLine " + izouSoundLine + " from " + addOnModel);
          if (permanentAddOn != null && permanentAddOn.equals(addOnModel)) {
              addPermanent(izouSoundLine);
          } else {
              addNonPermanent(addOnModel, izouSoundLine);
          }
          izouSoundLine.registerCloseCallback(voit -> closeCallback(addOnModel, izouSoundLine));
          izouSoundLine.registerMuteCallback(voit -> muteCallback(addOnModel, izouSoundLine));
      }
docs: adds an IzouSoundLine, will now be tracked by the SoundManager
  @param addOnModel the addOnModel where the IzouSoundLine belongs to
  @param izouSoundLine the IzouSoundLine to add