This is most definitely not a language. The language is Greek, as the article also states: "It’s the same as modern Greek — the grammar, vocabulary, and sentence structure all remain intact — but the sounds come out in high-pitched musical notes." So you're just encoding modern Greek in a different way.

You could also call it a register (as the article does) and group it with shouting and whispering, I don't completely agree with that assertion but either way it's most certainly not a language on its own, it's a way of speaking Greek.

> written language which is an encoding of language sounds

That is absolutely false. Written language is _not_ an encoding of language sounds. The International Phonetic Alphabet (IPA) is, but there's a pretty long way from written language to IPA. Written language is a beast of its own and it's lagging way behind spoken language, but it's not an encoding of language sounds. It's a way of encoding language, but phonetics and phonology has nothing to do with it.

The Greek language is very very close to an encoding of language sounds.

Maybe more of a medium of communication?