Been wondering about something for quite sometime. In songs that have spamming sections eg. Magical Sound Shower EXEX that has X and Circle spam, how do we tell how fast or slow we need to go? No matter how many times I practice this on songs I always keep getting either SAFE/SAD/WRONG. I don't need to know about the faster spams in Negaposi, 2D Dream Fever, Den Paradigm, Disappearance and Intense Voice since I know you need to be pretty fast for those ones, so pretty much any other song can count here. Even worse though is parts like in Step Foward and Depression of Cybernetics EXEX that add Slide notes into the mix. These are even more confusing to me.
Ummm... You literally just listen to the music. You might just need to work on your left-right coordination. try plaing songs alternating between hands all the way through, As for slides, I don't particularly like those thrown in with fast note progrssions either, but all in all it comes down to practice.
I don't know either what kind of answer you are looking for, beacuse that is something that you need to practice for your own like you practice a musical instrument. But it is as well a matter of patience, because all these things you see in the game doesn't work straight on few minutes, hours but days and weeks. Only depending of your own gaming experience, your practice times will be shorter. Or you can do that: Go to Practice Mode and play the spaming part at least 10min non stop each day until you can hit everything with COOL. No excpetion if you already can do it without any miss, only all COOL allowed.