the interesting difference between rock and "black music" is that in "black music" the bass is treated like its own independent (and very fundamental) instrument, while in rock, it's the "bass guitar"… a kind of guitar, and in many cases, an inferior one, relegated to standing behind the lead guitar and adding extra depth and volume by replicating the lead line.

then again, I think it was lonesome_d who offered a minor dissertation a while ago about the complexity of speed metal bass-playing…