line.dart

class Line extends AnimatedWidget {
  final Function(Note) onTileTap; //<--new parameter
  ...

  @override
  Widget build(BuildContext context) {
    ...
    List<Widget> tiles = thisLineNotes.map((note) {
      ...
        child: Tile(
          height: tileHeight,
          state: note.state,
          onTap: () => onTileTap(note), //<-- pass tap callback
        )
    ...
  }
}