For me, I think it comes down to isolating myself from unexpected stimuli while trying to focus. Listening to a video game song on loop, relatively loudly to block out external noise, is something that has worked well for me.
However, everybody is different. Do you listen to music / white noise / etc while working? If so, what's your go-to?
If I'm writing code or doing something active like that, the above applies, but add heavy metal to the list of things I might be listening to. But if I'm listening to metal it's almost always only bands and songs that I'm extremely familiar with (eg, have listened to a given song hundreds or thousands of times in my life) as those are less likely to be distracting to me, as opposed to something new where I feel obligated to really pay attention to the music.
One other option is I will sometimes put on a movie that I've watched many, many, many times (eg, The Matrix, Hackers, Antitrust, Tron:Legacy, The Social Network, Rad, Vision Quest, etc) minimize the viewer window and just have the audio in my headphones.
Very rarely I might go with some sort of basically "white noise" track like
"Howling snowstorm and crackling fire" https://www.youtube.com/watch?v=volQGswo3dg
"Cyberpunk city sounds" https://www.youtube.com/watch?v=x5zX1eRKEDM&
"Twin Peaks Double R Diner" https://www.youtube.com/watch?v=npVellnR6D8
"Coffee shop" https://www.youtube.com/watch?v=VMAPTo7RVCo (unless I'm actually sitting in a real-life coffee shop, which I quite often am)
etc.
I don't know if the sounds generated are actually helping or not (could totally be a placebo), however it's a seamless way to enter flow state, I've found. I've been using it for ~4 years now, and it very very rarely fails to deliver.
Also, I don’t mind playing two or more videos simultaneously by mixing different types, e.g. (ambience, asmr, music) in some volume combination. It helps not only to mask the environment, but with proper lighting may also take you to a completely different place.
If I am working on something mechanical where I know exactly what I need to do and it's only a matter of getting from point a to point b (like writing code in a familiar domain that I know like the back of my hand or writing tests) then I can listen to music or podcasts (although only podcasts that I am ok with missing large chunks off as I tend to zone out of podcasts if I am listening to them while working).
I've found SiIvagunner works well for this, they release like ~10 new song mashups a day and maybe half of them are good. Just load up some random youtube playlist consisting of thousands of songs and I won't recognize a single one of them.
But I can't have silence, so I get as close as possible by using a noise generator, and a set of earphones that really do block out external noises.
Just low enough to burble audibly and tune in if there's a song I want to pay attention to, and quiet enough to provide whatever white noise my brain requires for flow state stuff.
I've tried all the other things... and I don't really use albums or playlists because there's always something to contend with and invite the process of making choices. For me, it's best to either go "eclectic rock is working", and if it's not then "let's hear something more electronic".
Not having to think harder about it works well for me.
To avoid having YouTube website open while working and to maximize productivity, I use ytpodcast[0] to convert the youtube videos to podcast and add them to a listen later playlist and finally I listen them later on Apple podcast app on MacOS or iPhone.
If I really gotta get down to business, then it's one of their Liquid DnB mix shows. The high energy, repetitive songs that flow into each other really help.
Sometimes I'll even listen to music while on a call just to help myself focus lol
For parts where I have to think, I listen to nothing.
Sometimes I'm just not in the mood, and the heavy metal helps a lot with that. I can't really listen to it while coding, so I might just open a whole music video and see if it snaps me awake.
If the task gets more complicated, I drop the podcast/financial market thing. If it gets even more complicated, I stop the music.