I have some of the Art du Son cleaner. It works. I have 2 copies of a number of CDs and tried before and after cleaning comparing treated and non-treated. Before they sounded identical, after one was cleaned the cleaned disc sounded better. And expectation bias not relevant as I got someone else to play the CDs blind and I choose the cleaned disc more often than statistically random. My mate could not detect the cleaned cd, so the differences were subtle (but noticeable) and he has self-confessed cloth ears.