I got it to load one of my MIDI files, but the stock on they provide felt pretty glitchy. Do the sliders just affect the way the MIDI is visualized? Because it

I got it to load one of my MIDI files, but the stock on they provide felt pretty glitchy. Do the sliders just affect the way the MIDI is visualized? Because it seemed to break the audio up on their default file, but didn't change anything with the MIDI I uploaded. I just thought something was probably just broken on Firefox.