I think when I wrote the comment the butter bit was me just venting about the PJ interrupt since I played it again very recently lmao
It does admittedly flow with the kind of aesthetic the game is going for, dropped jaw and all from the crew around there. It really do be a different strokes for different folks kind of thing but it's even close to a deal breaker.
Same for the vocaloid voices, I think the vocaloids fit perfectly for the tutorial since it's a song with more unusual visuals. Hard to do a 180° on the others personally but hey, maybe voices for songs where they talk more and then vocaloids for the more unusual can be a good mix!
Tackling the surprise left hook from some notes is kinda rough though because of how big the display is for the notes. The note scrolling in works for single note lines but it would get a bit awkward for double note lines. For line transitions though like the dreaded Stir and Mix example, it's up to the stars for how that'll get looked at. A line preview would simply fill in too much of the screen or crunch the bar in an awkward way which it's just not formatted for. I don't know exactly how a note coming in would work for a line transition either stylistically. The quickest fix could be to be like Um Jammer Lammy but that game doesn't exactly have a style to worry about for the bar itself. It's a problem that really only applies to support lines with notes at the start of them too so we'll see what happens there.
I'm glad you liked the rambling though! Honestly this one of the first few times I've actually voiced a full opinion rather than just saying "game good / game bad" so I thought it was just EXTREMELY nitpicky / whiny at first. I guess that's just how review type things you write sound while reading it back when it's a bit opinionated. Melodii do be pretty cool though!