Your brain sometimes just leaves a placeholder and makes itself believe it was the real shit. Once I had a dream of a hilarious joke. I even laughed hard in my dream. I woke up, tried to remember the words immediately and it was gibberish.
It does work sometimes, but there's a good chance that you just had a dream about placeholder for one weird song, placeholder for another weird song and placeholder for mix, and the illusion just worked.
OR we're in an alternate universe where the famous composer of the millenium doesn't actually remember that visionary song, loses motivation and becomes an accountant. It's about fifty-fifty.