Gakupo+Megpoid(wip)--What Is Love?--Haddaway

Bear with me and this video since I am a Vocaloid N00b. Any tips? I have been relying on online guides and my ears thus far... see where that has gotten me? I was able to get Gumi and Gakupo to Engrish correctly-- but, as you can hear, their voices are rather flat. Also, there is one part towards the end that bugs me. The background music also causes much ear bleeding,. Art courtesy of Google (in due time I will load my own art to this video). What is Love by Haddaway