The "Fantastic International Music Festival" (ファンタスティック国際音楽祭, Fantasutikku Kokusai Ongaku-sai) was a festival in which Michiru Kaiou, Haruka Tenou, and the Three Lights performed at in Act 50 of the manga.
Michiru and the Three Lights played there in episode 180 of the anime as well, along with the New Tokyo Orchestra. It also was in the 1996 Sailor Moon Sailor Stars Musical.