The response you give right before a live/audition/fest seems to only increase Danketsu.
Dance Appeal, Kirame Kirari, No reporter, Normal mood (not that it matters, as long as both were under the same conditions).
On a correct response, Normal x1.0 gave 100 points, Burst x3.0 gave 330 points.
On an incorrect response, Normal x1.0 gave 100 points, Burst x3.0 gave 327 points.
One can conclude that a correct response gives 1 point of Danketsu. Either that, or one can conclude that you take a 1% hit to your Burst score, which doesn't seem likely. I suppose you could test for that too, but I'm pretty confident in the first.
A previous experiment showed no difference in the number of Perfects to full Voltage.
Also, a little tidbit about Voltage gain and songs. i (140 BPM) took 44 beats to a full meter (Normal mood, no reporter), Kirame Kirari (180 BPM) took 57 beats (Normal mood, no reporter). Coincidentally or not, 140 / 180 ~ 44 / 57.
EDIT: Reloaded my save, tried again. It does not affect Memory Appeal gain (both were 43 to a full bar after the appeal), multipliers seemed to increase and decrease at the same rate. I honestly don't think picking the wrong choice affects anything at all, except a point of Danketsu.
One thing I've noticed is that the lower you run the multiplier, the harder it is to get it back up. I think at around x0.50 or so, the multiplier was increasing at a good +0.01 ~ +0.02 (okay, that's not good), while at the higher multipliers (above x1.00?), I was pushing +0.03 ~ +0.04.
EDIT 2: Okay, now I'm confused. What does Mail Boost do?
EDIT 3: Okay, here we go. Waranappe the 10th, Kashimashi: 57 Perfects OR Memory Appeal + 33 Perfects = Full. Same amulet, Mail Boosted Dancing: 57 Perfects OR Memory Appeal + 31 Perfects = Full. Maybe there's a really small Voltage boost you get, it's hardly noticeable if there is. Various old stuff deleted to save space and confusion.
Apologies if it just seems like I'm just too concerned over stuff that doesn't matter much... and dang this got long. Sorry.