Vocaloid?
oh, yeah.
Someone will come along who can explain this better, probably. Vocaloid is "a singing synthesizer application software developed by the Yamaha Corporation that enables users to synthesize singing by just typing in lyrics and melody." -
[You must be registered and logged in to see this link.]There are a handful of characters, each with their own vocal range/gender for singing different types of songs.
A lot of people just mess around with this and have fun. Some people make it sing popular hit songs, or anime openings, etc. Other people use it to compose and hear songs before singing them themselves. Still others write advertising jingles with it, etc.
It's also a Japanese fan phenomenon. What seems to happen (and correct me if I'm wrong, guys) is that someone creates a song with Vocaloid. Sometimes it stops there and a bunch of people enjoy the song. Sometimes, though, it inspires someone else to create an animated music video for the song (sometimes several people...I think there are, like, six different versions of "Alice Human Sacrifice" AMVs floating around.) Or sometimes someone creates a song and an AMV at the same time.
There are SO many animated music videos floating around; from what I know, they are all fan-made.
Sometimes the songs are also covered by actual singers, so you'll see AMVs floating around that aren't actually the vocaloids singing anymore, either.
More info on everything in the wiki link above, and also in the Vocaloid Wiki:
[You must be registered and logged in to see this link.] Regular wiki has all the main facts, and the Vocaloid Wiki also has info on some of the fan stuff (for instance, there's a list of the some of the most well-known fan-made Miku songs/AMVs here:
[You must be registered and logged in to see this link.] )
It's popular enough that it also inspired a manga:
[You must be registered and logged in to see this link.]There isn't an anime. Yet. I'm kind of hoping for one, sometime in the future.