Easter Egg - Tamm the River King and Sona's Songs

So I was playing Sona earlier and I used her laugh while in the river. Her laugh makes her play chords. Anyways I did it twice in a row and the second time you could hear** Tamm make noise or something.** Is this a** new eater egg **or is it an old one that has to do with something else? Has anyone else tried this?