(Yeah, I stole Marius' style of writing thread titles, sue me

)
This is a piece I began mostly out of boredom yesterday at half past midnight, and finished about half an hour ago. It took a little over two hours to write, and is my first finished piece in many months. Like the title implies, it consists of variations on a theme, which isn't mine: it's a ballad by portuguese singer/songwriter Luiz Goes called "Poema para um Menino". It was traditional for composers to write variations on other peoples' themes, and that's what I did. The theme's arrangement is mine, though.
The violin part eventually becomes extremely demanding, but I felt it was needed to speed up listeners' heartbeats

the piano part also has its difficult moments, particularly the coda. I'm not a pianist, so advice regarding the piano part would be extremely welcome.
It lasts aproximately 7 minutes, and consists of theme, followed by four variations and an extended coda. Below there's a .MUS and a .MID file.
EDIT: Added the score in .pdf format