Yes you can play with Quantize and Humanize in Realband if you want.
To be honest, RB (and PT) are very good at MIDI editing.

If you only want to copy a certain note range for the new bass part, check out the Data Filter option.

When you click Copy, in the resulting pop up there is an option to enable the Data Filter and then you can select a certain note range (among other filters).
Same with Cut and other common commands. Let the Data Filter become your friend. smile
For MIDI it's another nice tool RB has that can save a lot of time/effort ..


Make your sound your own!
.. I do not work here, but the benefits are still awesome