L'épisode commence avec trois filles en train de chanter, se nourrissant de l'énergie négative des gens d'un café. Se plaignant d'avoir été banni, la leader, Adagio, découvre que de la magie équestrienne se cache dans ce monde. Adagio, Aria et Sonata vont alors tout faire pour obtenir cette énergie. Pendant ce temps, à Canterlot High School, un concours musical à lieu, Rainbow Dash, Pinkie Pie, Applejack, Rarity et Fluttershy y participent sous le nom " Les Rainbooms" avec Sunset Shimmer, qui souhaite réparer les erreurs du passé. Les 3 filles s'inscrivent dans le lycée et participent sous le nom " Les Dazzlings " pour gagner plus de pouvoir, en une chanson, elle envoûtent tout le lycée sauf Les Rainbooms et Sunset Shimmer pour faire un Battle Of The Bands, ces dernières appellent Princesse Twilight Sparkle pour les aider à vaincre les Dazzlings et rétablir l'harmonie à Canterlot High..
Rainbow is looking for a new drummer for her band and realizes that Pinkie does well on the drums as she does anywhere else..
Rarity is trying to move a grand piano into the band room for practice, so she gets the Diamond Boys to help her..
Granny Smith absent-mindedly sold Applejack's bass guitar to Flim and Flam's pawn shop, so Applejack and her friends confront the brothers to try to get her bass back..
The girls try to come up with a theme for the big party to be held later that night..
Rarity sings about her fashion philosophy..
Rainbow Dash needs to buy a new guitar, but when she and Trixie have their eyes on the same one, they have a "shred off" to decide who gets it..
Rarity helps Fluttershy volunteer at the animal rescue center to clean the hamster habitat..
The Rainbooms sing about their everlasting friendship to Sunset Shimmer..
Sunset Shimmer reflects on how friendship helped her become the person she is today..
Vinyl Scratch, or DJ-Pon3, puts on her headphones and listens to her favorite music as she stops by Sugarcube Corner Cafe on her way to school, while everything around her seems to react in time to her music..
