It makes sense if you think about how many of the nobles so far are interested in mainly appearances and status, while students interested in alchemy are more interested in making tools than appearances (look at their clothes this chapter). It's not really the music club, but rather the...
Figure out who you can trust as a friend. You also don't need to overshare and leave yourself vulnerable.
There's a huge difference between talking about a family gathering or your hobbies versus sex life.
From what I can tell so far, the Senpai likes Fuyuki who likes Eri. That’s the exact situation that Fuyuki is in where the person she likes is interested in someone else, and why Senpai needs consoling.