Wow. I really liked this.
The animation is great, the OST is awesome, and the characters are great too. What really impressed me is they actually animated them playing, something a lot of other music series shirk. Let's hope they keep it up. The character design is nice too, it feels way more like a movie than a weekly series.
I like all three characters. Kaoru has this kind of "everything sucks" attitude, but toward the end, you get a real sense that inside, he and Sentaro aren't different at all. They've already got a friendly, not-so-hostile rivalry going on. Once Sentaro called him out for being scared, Kaoru instantly fixed the problem that was plaguing him for years. He suddenly stood up against his own fear and just went with the flow. Sometimes that's all it really takes. Sentaro is obviously a win because he's so laid back, but really passionate about jazz music. Ritsuko is great too. I don't know why, but she overwhelms with this refreshing feel. We ultimately didn't see much of her personality aside from the nice girl who's childhood friends with the local delinquent, but there's definitely more to it.
The 1960s setting is great too, since it feels far more natural to be into jazz at that time than it would in more modern setting, like Nodame and classical. Like I said, the OST is awesome, like Cowboy Bebop, but more finely attuned to what's going on on-screen. I was thinking that this series was doing it better than Bebop. Which, when I looked it up, is funny, because Kanno Yoko is doing the music for this just the same as she did for Bebop.
Before I knew this series was about music at all, I was wondering what would bring Nanri Yuuka (Ritsuko) back to voicework (she left to pursue singing which she liked better). I guess that makes sense. Makes me wonder if Ritsuko sings.
I was thinking Rotoscope.