The song title – If You Do Do – is unusual, and I have no idea what it's about. Nevertheless, it's a nice enough visual feast featuring no fewer than nine Tda (said: "tee-dah") Vocaloid models.
That in itself makes it worthy of viewing; and I am also leaving it as a challenge to visitors to identify the nine, perhaps listing them from left to right in the comments if anyone should feel so bold.
I think this comes from the NicoNico ChoParty event (it certainly looks like it) but am not a hundred percent certain of that as yet. That concert had, yet again, an audience of thousands, which now seems to be the norm for these live performances.
The song has its (to me) odd-sounding moments, and gets cut off before the end; but this video does provide a strong flavour of how this ensemble works with this material. I found that, overall, it felt like a good production, though imperfect, but certainly good enough to showcase here...