Great reminder! I used to use brain.fm/. Their music is designed for reaching mental states. You can get more informations here: brain.fm/science
I had the luck to buy a lifetime membership for less than a year costs now when they were in their beginnings. But 50$ / yr is also fair in my opinion. I recommend to give it a try.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.