I'm a huge classical music fan. I play the piano a lot and I love doing so which is why I thought this series will be perfect for me, but I was sadly mistaken.
First of all, I would give the first season 8/10
The good:
Fast paced storytelling, heartwarming storys and a likeable protagonist and antagonist (if you can even call him that).
Beautiful music and it makes one want to play the piano.
The bad:
You can't really enjoy a piece of music since it will be cut of at any second. On the other hand, sometimes they go on for a minute even though you've heard it a lot already just to "show the reactions".
This is a big point, in a Manga you can write how it makes people feel but in animation, you should be able to feel that as well. which of course is very difficult, and they didn't really succeed.
The cringe-worthy:
The animation. It's a 2D animation with 3D when they play the piano. The movement of the hands is very pleasant and rarely seen in animation, but when the whole body is shown, it looks creepy and unpleasant. But after a season, I got used to it.
Season 2:
This season discarded almost everything good about the first and tried to better the cringe-worthiness by removing the 3D.
But, they made it worse. Now there are juist still shots shown of them playing the piano. Sometimes they are clearly playing with both hands and the still shows them with one hand in the air.
The fast paced story comes to a halt because the entire season is just one big competition and the animation gets so lazy they use still shots about 50% of the time. Did the budget run out? What happend?
The good:
The protagonist is still likeable and the music still good (except that it's now exclusively Chopin, which get's a bit boring after a few hours)
4/10
Overall 6/10
First season is recommendable, the second season not so much.