This genuinely excited me and kept me rockin' along virtually non-stop for some 38 minutes. It's the final part of a Vocaloid concert (I do not know where or when) that featured no fewer than eleven Vocaloid characters, more often than not with several on stage at once – eight in a couple of songs.
I recognised (alphabetically) CUL, Gakupo, Gumi, Kaito, Len, Lily, Luka, Meiko, Miku, Rin and Teto. CUL here seems really nice as a programmed character; and I could grow to like that one. I am aware of some imperfections with her voice in certain registers, but her rendition of World is Mine (to be found elsewhere) is extremely competent and sounds very natural.
I also noticed how well Gumi and Lily went together, whether they were singing their duet in the same octave or (as was done in parts) an octave apart.
One interesting effect of this multiple appearance is that the Kagamine twins are so obviously that much shorter in stature than their 'older' colleagues. They seem almost tiny next to the others! I have all their heights (and some other details) on file, and I think the difference is being exaggerated a little owing to different footwear (heels etc with the 'older' females), but the underlying point remains: they are actually quite small.
Despite a less-than-ideal technical quality standard (which seems to be mostly if not entirely down to the video-ing, not the performance), this is a very enjoyable video of part of a concert played to a packed house – just look at the shots of the audience – which only goes to show just how big a phenomenon this really is, out there in the world. Vocaloids rock, as the saying goes...