Okay, so I would like to critique this~! So start off, I like how you did the drawing and the shading's awesome, better than I can do shading, to be honest XD I also love how you did the flow of the hair, it's so pretty and bright *A* And the vocaloid outfit that you chose for Melody was a good idea!
The originality is good, with the pose and the other stuff. The technique you put into it was good! ^^ And last but not least, you did a very awesome job on this, no cons needed!
First off, this is really, REALLY gorgeous. You're definitely a very skilled artist. The colors are beautiful, the anatomy is near perfect, and the drawing is over-all pleasing to the eye. My only real complaint is that the shading looks a little too blocky in some areas (i.e. under the bust), and your style is a little generic. Also, I think that the picture would look better without the character's name in the upper right-hand corner. I feel like it takes away from the drawing as it's kind of distracting. Overall, you've created something really beautiful. Keep up the good work!