It's a Kyoto Animation show about a school band club. It's subtle, beautifully animated and doing what it says on the tin. Schoolgirls play in a band... and that's it. The show really is all about making music. They go to rehearsals, argue about their teacher and worry about who'll get selected for the concert band competition. If you think that sounds too low-key and everyday for you, then you're probably right. It starts quite slowly and it's got absolutely no slapstick, panty shots or wacky hi-jinks. It's much more grounded than KyoAni's other "schoolgirl musicians" hit series, K-On!.
It's mundane, but that's its strength. In the end, I thought it was clear, honest and excellent.
It's examining some traits that are very Japanese, but probably universal enough to speak to everyone. There will always be people who try to read the group mood and don't like putting forward their own opinions. They're self-effacing. They don't want to rock the boat. There will also always be groups where seniority trumps ability. Thus here we have a protagonist, Kumiko Oumae, who's indecisive and easily swayed by others. She's nice. She works hard. You'll like her. However she doesn't want to join her high school band club and she certainly doesn't want to play the euphonium again, yet both of those things come to pass because Kumiko is bad at saying "no".
However she grows over the course of these episodes until in ep.11 she's telling her friend Reina Kousaka to do what she wants and not be influenced by others. "It's okay to be a villain." This other girl, Reina, has always been disruptive, cold and uncompromising. She didn't care about being nice and as a result nearly broke up the band club. People found themselves having to choose between the nice girl everyone felt sorry for and the spiky one who's better at the trumpet.
This is directly because of their teacher, Taki Noboru. This translates as "climb/swim up a waterfall". Taki's a challenging character, despite his calm politeness, because he doesn't care about the comfortable way of doing things. He doesn't go with the flow. He goes straight for the music, although admittedly he does start by giving the club a collective choice: (a) play to win or (b) spend the year taking it easy. Right away they're having to vote. Not everyone likes that. He'll force you into every hard but necessary decision that group diplomacy would have avoided. He rejects everything about how they used to do things. He might look like a mild-mannered, slightly apathetic nice guy, but he's a bastard who'll have a go at you in front of everyone.
Consensus doesn't get things done quickly, or sometimes at all. Taki does. However by the same token he can be distant to a fault, e.g. being bad at pep talks. He's far from being a perfect character. However the traditional, hierarchical Japanese approach is also getting bloodily dissected in what happened in the club last year. Seniority was everything and a group of enthusiastic, talented first-years came to grief.
The girls are likeable and often flawed. (There are also a few boys, but they're a tiny minority in a mostly female show. Apparently the original novels end up giving Kumiko a boyfriend, but this has been heavily downplayed here in favour of girl-girl romance.) They can be cliquey and bitchy. However they can also be kind, generous and graceful in defeat. Kumiko is often callous and dismissive, but she doesn't mean it. Reina usually gives the impression of not caring about anyone. Hazuki is lovely and gets hurt. Midori is rather adorable, actually, managing to be timid and soft-spoken in personality but also a tough, single-minded warrior if she's behind a double bass. They're human. They're working together towards their common goal. They feel real and you'll care about them.
The theme music is great, of course. It would have felt wrong if it hadn't been.
This show isn't empty-headed cute entertainment. Its characters can quit, fail or be rejected. However it's also a funny, happy, feelgood show that I enjoyed more and more as I went on. It's very good indeed. However the storyline really is all about schoolgirls working hard at their music practice. The word you're looking for is "focused".