Synopsis: The bestselling, fan-favorite chapter-book series celebrates the magic of music! Jack and Annie have once again traveled back in time in their magic tree house, but they have a brand-new mission: to help bring happiness tomillionsof people. Their mission takes them to eighteenth-century Austria, where they're decked out in their craziest outfits yet—including a wig for Jack and a long dress with lots of ruffles and bows for Annie! But it will…