What kind of music do you think ASL would be into?
Hmm, so this is a question I never thought to really dive into before? But I like it! I hope you don't mind me giving you gremlin answers though Anon, because I immediately thought of a bunch of random stuff and with concussion brain I can't give a serious answer 😂 (going a little modern AU with this, oops)
Also this isn't edited because I'm answering it on my phone, and it's so late lmao
Ace
Ace has this whole badass aesthetic about him. So most of the time? He listens to different rock music. Classic rock, heavy, alternative, anything new and modern. As long as the song has a harsh beat, and sounds really really kick ass? He's going to love it. Probably has a million mixed CDs at his disposal that he'll pop in (he loves CDs because they're so classic) and will turn it on loud
On the other hand? When Ace is alone, he listens to a lot of instrumental music. Classical, covers of his favorite songs, soundtracks from movies and shows he enjoys. He's a badass on the surface, but underneath he's a soft boy who just wants to be quiet and calm. It helps him sleep better, and it also reminds him of all his lessons on manners from Makino
Sabo
Sabo has WEIRD music taste. If he needs to focus he'll use classical music while he's working on stuff. Otherwise? Very PECULIAR sounding dubstep and triphop, sometimes even fused with his classical music. The music almost makes no sense, but the synthetic and electronic sounds really Amp him up and he so so enjoys how cool they make him feel. He's had debates with Koala before about if it's considered "real music".
He also likes very obscure indie bands. Most of the time it doesn't matter in genre or vibes, if he likes the sound of this new up and coming band, he'll gladly be their first fan (which always seems to happen). He likes new, inventive, and fresh sounds and being able to introduce people to the bands he enjoys is huge for him.
Luffy
Luffy never really pays much attention to music honestly. If it's not some pirate shanty he's not interested very much in it and doesn't actually go looking for new music. But, he will listen to almost everything and anything, and it always depends on who he is with. Whoever he's hanging out with at the moment influences his tastes, and when he can really pay attention to it he'll find himself enjoying the music and tones. He's not super picky, and as long as a beat is catchy he'll get into it a lot and have fun.
The funny thing about Luffy though is that as soon as he's not in earshot of the music? He'll forget about it. A random song that Usopp made him listen to once will pop up in his head, and he'll bother Usopp to play it for him; and instead of describing it or using lyrics (which he doesn't pay attention to anyway) he'll sing the tone (which is off key and not anywhere close to the real beat) to Usopp expecting him to get it. (He doesn't)