Having finished the second Euphonium novel, I've become annoyed at the producers and publicity staff emphasizing the four girls for merchandising/sales reasons over the other aspects of the concert band. Euphonium's charm is its ability to weave tales from many members together into one narrative, but thus far Oohashi, Nakamura, and Saito have been content to only push Kumiko, Hazuki, Sapphire, and Reina (with the KyoAni Shop adding Asuka, Haruka, and Kaori). It really reeks of trying to sell this show to otaku and ignoring your other possible revenue streams (literally no Taki/Shuichi merchandise?!). I wouldn't be surprised if those three (and probably Hideaki Hatta) pushed for the additional content needed to space the first novel into a cour to focus on those four for the merchandising reasons alone.
This isn't a complaint about the work itself; I'm still immensely enjoying the show. I personally feel the other aspects surrounding it don't really depict the Euphonium novel as well as it could/should be. (And watching the first PV after reading the novel emphasized that back in March for me)