VOCALOID is a voice synthesizing application that have been sold commercially since 2004. VOCALOID began from the simple concept of synthesizing the human vocals for singing. From the start this was never an easy task for the programmers behind the software, but from that beginning VOCALOID™ has grown into a worldwide phenomena, spawning new musicians, albums, figurines and even concerts.
There are many different VOCALOIDs, such as KAITO, Hatsune Miku and Aoki Lapis, who sing in Japanese. There are also VOCALOIDs like L♀LA, BIG AL and Avanna, who sing in English. As of VOCALOID3 there are now VOCALOIDs like Bruno and Clara, who are Spanish, while SeeU is Korean and Luo Tianyi is Chinese.
There's an unlimited number of VOCALOID characters and if you surf the web you'll find an endless amount of VOCALOID songs, I had some difficulties finding some Songs that might represent VOCALOID to those who are new to it but I assure you this is something that can't be limited into a few songs it's immense and huge and diverse you'll have to go look it up on your own to fully grasp what VOCALOID is , if you have a few favorites that have not been included in the OP please go ahead and share them with us .