I like this manga, it's heartwarming and comfy. However, I have two main problems which kinda prevent me from fully enjoying it:
1 - God, the writting can be so amateurish. One "cute" is enough, we already know what Yori is thinking when you pan to Kino's smiley face before showing Yori's embarassed face. The writting should convey information we can't derive from just looking at the panels, and honestly, those panels would just be better with no text bubbles.
2 - This is something that always pisses me off about these manga: You have a plot where bands and music are really important, and both of the MCs, including the one who's a vocalist, don't have any interesting things to say about music at all. One of my favorite shoujo stories of all time was a side story on Ouran's manga, in which a girl gets more into rock/punk/metal music after hanging out with a guy who was kinda deliquent-ish, and they bond over it. As basic as it was, that's how it works for most real people. They tend to like some music, at the very least they can mention a genre they like over others! Music isn't my life, I don't know how to play any instruments, I can only take guesses at what makes certain genres different (like, I wouldn't really know how to explain the difference between "house" and other forms of EDM, or what math rock actually is), but I'd sure as hell be able to write better interactions regarding music than these ones. I get it if the author doesn't like music (altho as an artist myself, I'd die without music to listen to while drawing...), but you could at least do the minimal amount of research. Or ask a friend, or something. Idk. It's very frustrating.
Hmm, I see where you're going with this one and I get it. I, too, would love a love story that at least would have a sort of substance instead of mere psychological nuances of love-- a thing which by the way was done masterfully in Bloom Into You, there was never a dull moment. In the story, the elements of the stage play had a crucial role in establishing the foil against the antiheroine Touko Nanami--a weapon which Yuu Koito (the heroine in that moment) wielded against Touko's self-destruction.
So maybe, instead of just singing songs to Himari, Yori could just lure the kouhai further into her romancing by teaching her the basics of guitar, or something like that, something TANGIBLE that they could bond over. A THING that the kouhai could use to discover something about the senpai, and could help Kino in trying to figure out what and how does she really feel for Yori.
On the other hand, I also concur with what everyone else has stated about the matter that Music (probably, for now) isn't the focus of the story, not even music band dynamics (like Revue Starlight, a theater group dynamic, where both the subtext gay romance and theater are obvious).
I think we should just wait and see how their romance unfolds considering that there could be a love "square" among Himari, Yori, Miki, Aki. (Wait, they rhyme huh...???).