There are times when Quatre has played music in the series. We know that he likes to play the violin, since many pictures are shown with him and his violin together. But he also knows how to play piano. Apparently, Quatre explained that musical instruments help him relax and calm his heart. He's grown fond of music since he was a child. He plays with emotion. When he is happy, the melody will be happy and cheerful. When he is sad, it will be a very calm and slow tune. We can say his music reflects his emotions.
If you asked me what is Quatre's hobby? I would have to say it's drinking tea. Yes, that's right. You're probably thinking how can that be a hobby? I'm telling you yes it can! If you take the time to enjoy and savor the taste of each drop, it can be a hobby. This is true since there are many times we see Quatre drinking tea. Even more than playing music!
As we all know, Quatre shows some favouritism to animals especially dogs. Heero even said the dogs liked to play with Quatre more than him. He said something like, "Dogs can sense when a person is kind." So Quatre agreed and played with them. The dogs seemed to like him very much. I think it just goes to show you how kind Quatre really is. ^_^
Overall, he just enjoys nature. He even said how beautiful the flamingos were on his gundam. That's not exactly what he meant though. He regarded the earth as a beautiful living thing.