Canterlot High is hosting a musical showcase, and Rainbow Dash, Applejack, Pinkie Pie, Rarity, and Fluttershy are to perform with their new band, the Sonic Rainbooms. But another girl group, the Dazzlings, arrives and persuades everyone to turn the friendly showcase into a Battle of the Bands. As tensions mount between the acts, Sunset Shimmer realizes that the Dazzlings may not be ordinary girls and are after far more than just the title of best band.