So, fun fact, when most people are able to recall whatever incredible idea or artistic vision they had in their dream, they soon realize that it was just their memory replaying something that already existed. An obscure song that you forgot about, a scene from an old movie that you’d think would make for a funny comic strip, etc. Now, this doesn’t mean that people aren’t creative and can’t dream of new things, it just means that your dreams just churn out a vomit of things you’ve processed before.
I was going to object, I've definitely heard songs in my dreams with fully comprehensible lyrics. I've woken up and immediately googled the lyrics and couldn't find the song at all. I found one with the same title that I had heard of but it was completely different.
The closest I've gotten to randomly coming up with music like that when awake is by singing songs in a different tune, but even then the tune was metrically the same. Came up with some bangers doing that, actually.