>>1 OP FYI I highly recommend you look up who the bands that do the songs for anime openings and ending, this will likely save you sometime when trying to talk to someone about them, as there is no such thing as anime songs, just songs that J-pop bands do that go with anime openings and endings.
Vocaloids is it's own music brand and band of artist, and just use anime style characters for their videos, mainly because it's J-POP.
also this should of really been posted in the Music area, as bang✫bang said.
/saged