First of all; I loved the game! I actually enjoyed it more than some of the commercial games I have played and you definitely deserve a review.
The character design, both visual and written, was great. The story focuses on the two main protagonists (three, if you count the orchestra) without involving many other things. The conflict provided was great for discovering more of the characters, but it does focus heavily on this character development. People looking for well-written characterizations, cometh to this VN! The design of the characters underscores their personalities, which without the excellent writing could have seemed stereotypical, but instead adds another layer to their person.
The CGs add to the story, rather than just being an excuse to draw something pretty. Some people might balk at the differing drawing styles, but I personally found no problem there. The slides before every chapter, I adored. The stark black/white sketches somehow really reminded me of sheet music and went well with the music theme of the VN. The drawing style was also very attractive.
The GUI colour scheme was appropriate, as are the fonts. I would have to agree with an earlier post that the save and load screen had slightly overlarge lettering.
Loved the music theme, but agree with the quality of the recording. I sometimes hear a strange sound, but do not know what could cause this aside from microphone troubles. Again though; I really LOVED the music. The quiet piano melody was soothing and not disturbing during reading.
The backgrounds I was indifferent to, they did not stand out to me as good or bad, which must mean they did their job.
Review parts that might concern the content of the game are below:
I adored the running theme of misunderstanding; from the language barrier, to the differing attitudes of the main characters and the orchestra, and the relationship between father and daughter. Even the contrasting appearances of the main characters tie into this theme. It was lovely and made the story thematically coherent and engaging. Sometimes these misunderstandings were used humorously and sometimes more seriously; this really balanced out the emotions.
I also commend the bravery in the team for using two languages without providing a translation (unless you finish the game that is). I do appreciate the translation feature, but it was not necessary to the story. Using two wildly different languages really bangs home the difficulty in overcoming a language barrier and how much effort the main characters put into trying to understand each other. This understanding of each other despite their speech is magnifies the fact that they are also starting to understand the other as a person. It really it a lovely and important issue you have touched upon in your VN.
Altogether, If I would like to see things improved it would just be some polish of the GUI, the backgrounds and the music. I personally would not change the CGs, since I like the look of them as they are. I also had no errors of any sort on my Mac laptop, so the coding seems to be perfectly solid on this platform.