Siren is denounced as the leader and runs off, with Bassdrum becoming the new leader of the Minor Trio. Meanwhile, Hibiki and Kanade decide to enter a music contest together. On the day of the contest, they realise they don't have a piano to perform on, but their friend Waon Nishijima helps them out. However, it is soon revealed that the contest is a trap laid out by Bassdrum who spreads the Melody of Sorrow and creates some Cymbal Negatones. As Hibiki and Kanade struggle to fight against it, a mysterious masked Cure known as Cure Muse appears and ensnares the Negatones, allowing Kanade to purify them.
今日はなんだか、商店街がとってもにぎやか！
あちこちから、歌声や楽器の音がきこえてくるの。
そう、あしたは加音町の「音楽じまん大会」！
響と奏も2人でいっしょにピアノの演奏で出場するんだ！
当日、とけい塔の前のひろばには、楽器を持った人たちでいっぱい！
いよいよ大会がスタート！
ところが…ステージには、トリオ・ザ・マイナーのすがたが！
音楽を愛する人々を悲しませるなんてゆるせない！！
響と奏はプリキュアに変身して、ネガトーンに立ち向かう！
…でもこんどのネガトーンはてごわく、プリキュア大ピンチ…！
そのとき、どこからか美しいオカリナの音がきこえてきて…。
