I wear noise-cancelling headphones with background music for focus during a majority of my working hours. I have a "flowstate" playlist on Spotify which I've curated for a few years, from which I've more recently carefully extracted only those tracks which I can happily put on individual repeat for a particular flavor of focus. None have words to distract, nor sudden changes; all have enough of a beat or groove to help boost my energy. I made this "Flowstate: Repeatable FTW" playlist publicly readable:

https://open.spotify.com/playlist/6UScdOAlqXqWTOmXFgQhFA?si=...

Enjoy! :)