Vocaloids are virtual Japenese singers. Most songs can be found online, and Japan has live shows where the vocaloids are projected. Alex, Madison, and Alia all like Vocaloid, but Allena is the most obsessed.
Vocaloid is a software developed by the Yahama Corpoation. Each character is based off of voice acting, then synthesized to any given melody and lyrics. Characters are then named and given art. Vocaloid launched in 2003, and V3, the most realistic version yet, came out in 2011.
Currently, there are over 80 official Vocaloids. The most popular and well known is Miku Hatsune. She first made Vocaloid popular when she was released in 2007.