I think 3 or 4 parts wasn't enough!
You could have added some spice to the song, in my opinion. You should add things like (soft) drums or strings. I think the song doesn't convey it's message well enough. The message I get from this song is "someone practicing piano." Also, sounds good as a loop, but I don't know what you would use it for.
Don't take this review as a "I HATE IT", more like a "Try this...".