I should also add, though, that bass being "up front" or "in the background" has little to do with how complex its music is. Either way can be simplistic or complicated.
This is key to me. Play what serves the song. There are certainly songs where complex technical bass drives the song and other songs that are driven by a simple groovy bass line - play what works for the music you are playing.
Here is a a great simple bass line that drives the song:
If you added to this - you would be taking away from it.
