public static function constructFromArray($props) {
        $notes = array();
        if (isset($props['notes'])) {
            foreach ($props['notes'] as $note) {
                if ($note instanceof Note) {
                    $notes[] = $note;
                } else {
                    $notes[] = Note::constructFromArray($note);
                }
            }
        }

        return new Chord($notes);

    }