The book "Always Coming Home" by Ursula K Le Guin is an anthropological account of the Kesh, a people that "might be going to have lived" in future California. It includes short stories, songs, poems, recipes and sacred texts of the fictional people; but relevant to the question is the section at the end of the book which contains the script, numerals, and punctuation of the language, as well as an extensive glossary. I don't think there are any details on grammar written there, but there are example sentences in different places in the book. So, my question is, is there anyone that has tried to learn this language or studied it much? And, if so, what is it like?
I have the novel, but haven't yet read it, so can't say that I've tried learning Kesh.
I used to (and may still) have the cassette tapes that came with some work about the Kesh. As I recall, it was recordings very much as you describe for the texts: songs and lore of various kinds. As I recall it was a pretty sounding language. I think this is it.
I think it's therefore safe to say sòmeone has tried to learn it! Well enough to record it, anyway!