Vocaloids are singing voice synthesizers. Each Vocaloid program is a different voice, listed by a name and number. Each Vocaloid also has an appereance to them.

These are the main ones most people know about, I'll update more but also, These are the live performances. :3

Hatsune Miku - World is mine

Luka Megurine(by far my favorite) - Luka Luka Night Fever - Changed the URL because this concert was better

Rin and Len Kagamine - Butterfly on Your Right Shoulder

Rin - Meltdown

Luka and Miku - Magnet(My favorite vocaloid song)

Luka(Again) - Just be friends

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Not live

Kaito, Miku, Luka - Acute

Miku - Online Game Addicts Anthem WAITED FOR THIS TO BE ON YOUTUBE FOR SO LONG

Rin - Tokyo Teddy-bear This song is kinda messed up to me o.o

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Some also have English as well but they aren't that great, reason I didn't bring it up til now.

Luka - Radioactive(Cover) I listen to a lot of the English ones... this was the best one so far.