Mermaid Summoning Song

I don't know if this has been suggested before, or if it is even a good idea, but hear me out. I think it would be cool to be able to instead of just having a mermaid pop up out of no where, the player would have to play part of a song that is only playable while in the water to summon a mermaid. This would be good for people who need a quick mermaid (still would need to play like 10 sec of song) and those who don't want a mermaid to spawn.