Not only
NTR/NTT... for custom style creation, the whole
SFF Edit section is crucial to understand, to make style sounding exactly as we wish.
Author of this video explains NTR/NTT pretty well, although at beginning he should have used the same (piano) voices on both channels. That way it would be easier to notice the differences in resulting key sequence. But he decided to use Glockenspiel voice on 2nd channel and so comparison can be confusing if we don't know on what we should pay attention.
The whole thing is explained good enough in
Reference Manual (page 27). But funny thing is (as usually is the case with manuals), we can understand what's all about only if... if we already know what's all about
What I'm saying is, the only way to learn is to try on keyboard while having manual by side.
Bogdan