That adjusts the output from the SI Bass synth. The actual MIDI data is unaffected.
It also changes pitch for the entire track. If that is what you want it to do, that's fine.
You can get control of the MIDI by switching to the PRV. Here, you can play with individual notes or patterns.
You can drag a pattern up or down to play different notes for more variety and realism.
You can also add/delete/move individual notes.
Those patterns give you something to start with, and you can create something fairly interesting just using them, but you have the ability to manipulate them into something you can call your own.
PRV is your friend. Check it out.