private final void changeNumbering(final Set<Path> selection) {
		final TreeSet<Path> selectionFiles = selectFilesOnly(selection);
		for (final Path song : selectionFiles) {
			final SongChangeData data = get(song);
			final NumberingGUI plugin = new NumberingGUI(data, this.io,
					"Renumbering");
			if (this.master.isInterrupted()) {
				return;
			}
			this.io.handleGUIPlugin(plugin);
			if (this.io.getGUI().getPressedButton() == Button.ABORT) {
				this.master.interrupt();
				return;
			}
			plugin.copyFieldsToMaps();
		}

	}