this is what i do, and i'm sure a lot of people do it as well... i play a 4 string bass, so i put my E and A strings in the mpc and tune up or down to create an internal bass inside of the mpc...then i turn the freq down to like 10(gives me that deep deep sound) and note off... it's easy for me that way cuz i can read bass music so i usually put 14 frets in the C bank with a fretless E and A string and a couple B string frets...(E string tuned to +50 on the mpc is actually an A string)