Sometimes I feel like Jeff would unironically listen to Taylor Swift. Specifically some of her older songs. He'd likely lie and say he's listening to Green Day or something, though, which is most likely also on his playlist, but songs like Bad Blood and Blank Page would definitely be on his playlist
Toby would love Nirvana, Green Day, P!ATD, FOB, TØP, and so many more. Mostly groups known for edgier songs or alt rock, with some occasional upbeat songs mixed in. Singing/humming along to music would probably even grow to be one of his healthy coping mechanisms (totally not forcing one of my coping mechanisms onto him). I sometimes see headcanons that he wouldn't be that great at singing, but I feel like he'd most likely just not like singing in front of others
Ben would absolutely listen to game soundtracks constantly, but he'd also be an enjoyer of lo-fi and song covers. He'd likely also have some actual bands in his playlist, probably some edgier songs. He'd probably even find ways to do covers of some of his favorite songs in Majora's Mask
LJ's playlist is absolutely just circus music and ICP. That's it. Nothing else. Why? Because he thinks it's absolutely hilarious and he loves seeing people's reactions when he puts his playlist on shuffle
EJ likely doesn't always listen to music, but his playlist would consist of classical music and roughly what you'd expect in terms of songs with lyrics. It gets extra jarring on days where he's listening to music while stealing kidneys/taking care of the latest person to get injured at the mansion, especially if they need some sort of surgery and he doesn't feel like putting them to sleep first. Classical, metal, rock, rock, classical, rock, metal, maybe a pop song or two, etc. You'd never know what to expect next and it's always a fever dream with how often it jumps around. I mean, imagine getting cut open with Mozart or Bach playing in the background
Let's be real here, Nina's would be a mix of pop, alt rock, and V-Kei. She likely listens to groups like JILUKA (great band) and put them in the same playlist as Katy Perry, Ariana Grande, Avril Lavigne, Mother Mother, and a few others. She would also absolutely try to learn Japanese just to sing along to some of her favorite V-Kei songs
Sally would have a playlist of entirely songs from her favorite shows and movies. This little cutie would definitely be a huge fan of Disney, Pixar, DreamWorks, Nickelodeon, anything suitable for her age. Tim and Brian would absolutely steal whatever Monster High movies (the series of movies that ended with Boo York, Boo York specifically) they can find just for her, as well as all of the classic Barbie movies. She would be singing her heart out and everyone around her would know immediately to stop what they're doing to either sing with her, especially when there's a masculine voice because she gets a bit upset that she can't do it right, or to cheer for her when the song ends
Might make a part two to this if I remember. Contributions are appreciated