Watch Princess-Session Orchestra - Episode 1

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)