BMS is essentially what Stepmania/ITG is to Dance Dance Revolution, but for beatmania and beatmania IIDX. 5key and 7key modes are available + turntable, most of the available charts utilize it. BMS is pretty hard, just like IIDX, but it's a lot of fun if you get used to it, especially with a dedicated controller. Anyway, here on this page you can download all the BMS charts I made since late 2024. A BMS player is required of course, I can't exactly think of the most definitive one out of them all, but currently I use Lunatic Rave 2. Qwilight is modern and has Steam integration, while Lunatic Rave 2 is a beta game but with a lot of available content like skins. If you wanna learn more about BMS, I recommend you to check out the BMS Community Resources website. And yeah, I wanted to give another quick warning: many of the charts that are present here are NOT GOOD, but I still wanna keep them here at least for archival purposes.
Enjoy!