There was obviously a lot of effort put into the animation, and music, but was there as much effort put into the story (and voice acting for that matter)? I'll start off with the voice acting: it was extremely unconvincing, and laughable. The voices also happened to take me away from the music, so you probably would have been better off without them. On another note (pun intended?), why is he playing piano while his parents are fighting?
Then his dad leaves, and, "The Composer," decides to roll, oh wait, DRAG his piano onto the side walk so he can... play piano outside. Why? While he's playing a bum happens to stroll along - by the way, what kind of place does this guy live in where hobos are just strolling along the sidewalk? So the guy gives him some cash, but before that, the Composer closes his eyes, clench his teeth, and starts whimpering. Am I supposed to be moved by now? Then, my favorite part, the bum looks up with a smile, a tear in his eye, and the Composer plays a nice little chord - classic. Then I guess the Composer says to himself, "Well shit, if I can impress some random hobo on the street I must be amazing," and drags his piano all the way to the city to play for all the people who couldn't care less. It's at this point, some guy talking on a cell phone rolls open this paper saying, "The Composer," which of course implies that he is instantly famous. Then some more instruments are brought into the mix, and the Composer's job is now limited to holding one hand on a music stand, and waving his arm around on the beat. Oh, and why are everyone's eyes closed? Shouldn't they be reading the music?
Only now, after God knows how many years, people start to realize that this, "composer," has been playing the same song the whole time! And then the song finishes, so he decides to walk home. The part where he passes the heavy metal show seemed a little unnecessary to me, keep in mind I'm not just saying that because I'm trying to defend that genre of music, which I'm not. So the composer arrives home, and discovers that his house has been abandoned. He turns and notices a sad boy playing his guitar. He gives him some money, starts crying, nice face by the way, and sits down next to him.
In the end, I think what basically ruined the flash was that you tried to hard, and it shows. The fact that the story is so stupid helped kill it for me as well.