In some sessions a few bass players are called to do what they do best. example when Marcus Miller, Maurice Fitz, Andrew Gouche are called, I guarantee you they have Cart Blanch. Listen to some of their work. Now on the other hand you have bass players that are called just to get the job done & thats it. They are asked to just play what fits. So thier hands are tied, they just give the producer what they want. I myself like both scenarios. The first one, the bass player puts his own stamp on the song & you know immediatly who that bass player is. But when the average bass player has to learn the song, or when that song is done live, to keep they same flavor of the song, you have to actually play the song almost ver batum, with a little variations. Now the other scenario, gives you more room to work with. Some producer like to leave some space, so when played live, who ever the bass player maybe can add his own fills when needed. so don't be disapointed. Look at it as, if you ever get a chance to play any of Marvins song or any other songs with that same philosophy, you have the room to make that bass part come to life with your own embelishments.