First of all the things I liked about this drama:

◇the Ha family before the time-travel
◇portrayal of deaf people and their struggles
◇Cheong-Ah as a character
◇Eun Gyeol as a child and teen
◇the relationship between Eun Gyeol and Choi Hyun before the time-travel

Now to the things I did not like. They tried to put in as much plots, subplots and storylines as possible to make it shiny, the problem was though, that the quality dropped because of it. It's like trying to learn 5 languages... you will be mediocre at all of them instead of choosing one and using it perfectly instead. So what was this drama trying to be? A story about a boy who is a CODA? A story about music, passion, teenage dreams? A time-travel story?
After choosing that, they again had to choose on which character they wanted to go with. Eun Gyeol? Lee Chan? Cheong-Ah or even Eun Yoo? It was all over the place and like that, the story was half-heartedly executed. And even with all those plots, subplots and storylines... it was still boring. It was predictable and not a special drama to remember in the future.

There were characters without a real purpose and who did not even get introduced properly, like the people who would dine at grandmas. And then there was Eun Gyeol who I felt like was carrying the whole drama. The screenwriters must have realized this too because in the last 2 episodes, his character got cheesier and out of character lines.

The characterization of Lee Chan was not the best either and he was one of the main leads. In his old form, he is way different character-wise and this is not something that can be explained with age or trauma. Old and young Lee Chan were 2 completely different people and I couldn't put them together. Also the casting of Choi Hyun/master. All 3 actors were so different from eachother... it was just not good.

The ending was not executed well either. Eun Gyeol and Eun Yu arrived in the present and it had no consequences. The parents didn't recognize Eun Gyeol and Eun Gyeol himself got all his memories from his first life. It just felt like lazy writing.

I was trying to find reasons to love this more, but sadly I couldn't.