I have 10 sliders on my i30 counting the master slider and I use them often with the 20 or 30 midi files I use. I don't have the knowledge or time to adjust the volumn on the midis and these slider work great.

I can't comprehend a keyboard with two volumn sliders. They must take a lot of adjusting of the midi files to get them to play the same. Sometimes I just have to tone down the drums. It takes a fraction of a second with the slider for the drums.