Harmony Island? The hell?

I went to Harmony Island today to get the song i NEED for another quest, but i didn’t realise how stupidly rng it is, it’s from a chest and not a quest like literally every other song in the game afaik, not just that it’s an adventure island so it’s only once per day WHEN IT’S ON, and yes, it’s only one once per f*cking week?! This is beyond stupid.