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.
Here's a tip I picked up somewhere. Make a playlist. An hour or two worth of music. ONLY listen to it when you're studying. I've found my brain just blocks it out after a few times through, but it triggers my subconscious or something. As in, if I'm not feeling like studying, I put it on and my brain just goes,"OK, it's time to study." I change it up when I'm starting a new long task (writting a new book, starting a new semester, whatever). At first, I find myself listening to it, but it doesn't take much repetition for it to fade into the background.
Not really a album but MyNoise.net has a lot of good generators for background noise. Radio Free Fedi's Comfy channel also is great for chill study music, and it only plays indie artists that have Fediverse accounts with links to the artist support pages where you can either buy their albums (or songs to build your own piecemeal) https://radiofreefedi.net/.
I just added a bunch of classical to a playlist and then removed the occasional piece I found distracting. I still use that playlist when I need to focus.
I like listening to video game music when studying. I heard somewhere that game designers use their music to keep you playing their game and lose track of time and hyper focused.
Atomos or the self titled album by A Winged Victory for the Sullen
Almost anything recent by Carbon Based Lifeforms but Alt:01, Alt:02, or Stochastic especially
Loscil is great but not a single album stands out though Submerz and Endless Falls are smooth
Hammock's soundtrack for the movie Columbus
Brian Mcbrides The Effective Disconnect
I would recommend Stars of the Lid, but they are too sleepy for me. However, when Brian Mcbride and Adam Witzie do their own thing it is usually less sleep inducing-
Don’t do albums or long playlists, because every time it ends you’ll realize time has passed and you’ll stop studying. Instead pick a song or two or three and just play on repeat so you lose track of time. But if you must, then Toxicity by System of a Down.