I had fun taking this quiz and trying to get a good score. My first attempt scored 577 and attached is my best attempt after around 6 plays.
I initially was going to try playing this in the itch.io desktop app as a local file but it seems to have some sort of error messaging saying "The following features required to run Godot Projects on the Web are missing: Cross Origin Isolation - Check web server configuration (send correct headers)" so I wanna guess it needs some sort of live internet connection? Not 100% sure about this as I ended up playing it on Chrome.
On another note, regarding the gameplay, I kinda felt that the fade in for the song previews could be a smidge faster while the fade outs kind of dragged on a bit longer than I expected. Not sure if that fadeout time is actually the time for it to load the next song.
I do like clicking on the respective talent to answer the cover but at times I kinda played myself hovering past the correct talent when going side to side to answer. A hotkey function from what another comment mentioned also seemed like a good idea for speedier answers.
The current song playlist consisting of covers is not bad since it's a decent challenge with how many talents sing the same songs but I was wondering if implementing originals would take time a lot more time compared to covers or not? Because if it's related to sourcing a YT link and getting a thumbnail then the talents and hololive IDOL project have their respective YT Music Topic Channels and it's not that difficult to extract the art from their Singles, EPs & Albums. I think adding originals would give the playlist more variety on top of the covers or even have separate modes based on covers or originals; a sole talent, generational group, concert playlist or all random. Otherwise if you plan to just do covers then that's totally understandable.
I personally just had my own concept of a hololive music quiz brainstorm a couple days back and remembered playing your hololive cover quiz a while back and been meaning to check out what system was used for this.
Best of luck with future updates!