Boom Boom Rocket

From Bizarre Creations regarding scoring: http://www.bizarrecreations.com/article.php?article_id=5286

Basically, in terms of accuracy, the note hit ratings are weighted:

"Perfect": >95%
"Awesome": 80%-95%
"Good": 40%-80%
"OK": 0%-40%
"Missed": 0%

Since the patch, letter grades are solely keyed off of this accuracy weighting scheme of *all* fireworks. 90% is the cutoff for an A. The accuracy rating displayed at the end of the song *excludes* missed notes, however, so, yes, if you miss notes, you will need the displayed accuracy to be correspondingly higher to compensate.

As White Shadows and Sovietaced have mentioned, hit ratio + accuracy = 190% is pretty much the formula. It's actually (very slightly) more lenient than that, due to the math involved in the weighting, but you are almost guaranteed not to notice in practice.*

In any event, you probably should be getting 100% hit ratios regularly on the song on which you plan to aim for an A. Although that's not strictly necessary, I've never come close to the requisite accuracy on a song on which I can't get a 100% hit ratio.

"Smooth Operetta" has the fewest rockets and the slowest tempo, so, in that sense, it's the easiest (and thus, a common recommendation). However, it might be a good idea to run through all of the songs at least once or twice to find out whether you personally find other songs easier, for some reason.

Since score has no effect in and of itself, don't touch the bonus multiplier if it distracts you from getting a lot of "Perfect" hits. If you don't touch the bonus multiplier in "Smooth Operetta" (leaving it at 4x throughout), you will need, as a rough guideline, about 6 million points for an A on Medium.

* Hit ratio and accuracy are actually multiplied, not added, and the result needs to be >=90%. As an example, 95% + 95% = 190%, but 95% * 95% = 90.25%. Again, the difference is so small that you are not likely to be helped by it.

I find the easiest song to get 100% hit ratio and still get over 90% accuracy is Valkyries Rising, because it has a slow tempo and the notes keep in time with the song.

They changed the ranking system after the patch. What you want to shoot for is a 100% hit ratio and at least a 90% accuracy. That will get an A. Or you could get 98% hit ratio with a 92% accuracy. You get the picture. Good Luck.