I think this is a really good answer. Just search for a focus playlist on whatever platform and let it run.
If I’m picking out music more specific, I find myself thinking about that, and what it’s like, and if it’s helping, and maybe I should hey this other album or artist.
Don’t let picking the music distract too much from focusing on what you want to do.
Makes me think of high-score runs, mainly in arcade games. Have to play for a long time, and eventually you get stopped by a kill screen.