If you search for the acronym MMD on Niconico or YouTube — the two most popular video-sharing sites in Japan — the resulting list will have over 100,000 anime videos, most of which have 3-D anime-style girl characters singing and dancing to electronic J-pop music. What's surprising is that these (usually short) videos are not created by professional anime studios; they are mostly made by amateurs.
MMD stands for MikuMikuDance, a freeware animation software that has taken the Web by storm. The tool was originally released online in February 2008, with a very limited set of features that enabled users to animate a 3-D model of Hatsune Miku — the mascot character for the artificial singing software Vocaloid, which was released six months earlier in August 2007 and generated a boom in indie idol-music compositions on Niconico.
Using MMD, PC users can easily program how a 3-D model moves its hands, arms, legs, lips, and so on. To make a music video, users simply add a song and sync the model's movements to the beat and lyrics. Although MMD lacks versatility compared to expensive commercial tools, it has the essential advantage that the 3-D model immediately moves according to whatever movements you specify, making it very easy to use.