"mapping out the bassline"

hi. lately i've seen a video on youtube and the guy who's making a beat there is saying something about "mapping out the bassline "

http://pl.youtube.com/watch?v=vNprYdecnQo

(btw his beats are awesome check it out, especially this one, I've been listening to the infamous mobb's "pull the plug" for over 2 years now and still I'm crazy about the beat and in this video diskodave makes a beat from the same sample and now i don't know which beat is better hehe they both are crazy bangin' )

I don't really know what's going on there cause it seems as if he took the lowest note of the sample and his mpc created him a bassline of the same note...is it possible?? if so please tell me how to do it or give me another tip how to find the note of a sample in order to fit the bass of the same note. lately I had some problems with it. I always do it in such way that i just try all the notes and play these notes that i think are correct but this video made me think that there is another- easier way of doing it. peace!!!!

he just used the simple 16 levels=pitch, for the bass sample, and seems to have the original pitch near the top few pads, so that any keys he plays are shifting the pitch down nearly up to an octave, and then theres no higher/shorter notes, only lower/longer notes played - which helps give the illusion that theres not really being a cheapshot sample used.