PRINCESS-SESSION ORCHESTRA

The anime takes place in Alicepia, which is a mysterious country that has existed since ancient times. The inhabitants of Alicepia, the Alicepians, are a fun-loving people, but one day mysterious monsters called Jamaock appeared to threaten the peace of Alicepia. The story follows a trio of "princesses" who never forget the song in their hearts, even when facing such danger and step up to save the day with the power of music. (Source: Anime News Network, Crunchyroll News, edited) — Description from AniList community (anilist.co).