Does the Ocarina have a functional use asides from playing a random tune whenever you whip it out?
According to Gamerevolution it is just a Legend of Zelda Easter egg that plays a random tune.
Created using clay, a fairly valuable resource, the Animal Crossing: New Horizons ocarina requires quite an investment to craft. After putting in all that clay, surely the ocarina has some secret function and benefit? Well, it plays music…
Yep, at least at the time of writing, the only purpose of the ocarina is to play a tune. The ocarina plays random notes, with the player unfortunately not able to influence which sounds are used. It’s just a random song.
And corroborated on the animal crossing wiki
It is made from clay, and plays random notes when interacted with. The relevant button can be held down to hold a note.