So my question is do you find it as difficult to move past the demo as I do when you get one with a bassline? Any helpful hints for it?
Jimmy that's a great question, and there are as many answers as there are clients, I think. Sometimes I think you need to be part psychologist to figure it out when you're working from a demo.
I've had many times been told "oh, it's just a rough bass line, ignore it", only to find out when I did so that it had actually become the way the client/producer heard the line, and THEY were the ones who were stuck on it, not me, even if they didn't know it. That's where you walk the fine line of capturing mainly what's there and adding your own touches, so both parties feel like winners at the end of the session.
Something to find out right up front is whether the demo really captures the "feel" that's wanted, or was it just played through to capture the parts. A lot of that to me has to do with the drumming/rythm guitar tracks if there are any. I'll usually explore that with the client... "is this really the drum/rythm feel you wanted, or how about this..."? That can tell a lot, because if the client's not married to the feel that's on the demo, that opens up a lot of running room to ignore the existing bass line (assuming you'd like to), or even tear up the sheet and start over. On the other hand, if the feel's locked in, your options are back to #1 above.
Then there are times when I feel like you... I listen and say, why would you want me to change that? Sometimes that question can help the client think about why it is they wanted something different (you) in the first place and force them to say something... anything, that's helpful... or other times they just knocked some bass line out offhand and all they really need is for a "real bass player" to say, "Hey, that's already a cool line" and then they feel better about it...
...and I've had more than one situation like that end in: "yeah, the line's cool but I want the bass technique improved" ...and that's OK, I can deal with that vs. trying to be "different" if you've got a great line already written to a decent rythm track.
And finally, I agree with Justin or whoever implied "take the bass track away and I usually come up with something of similar vein but with my own personality"... I find that's true, and sometimes the client likes the result and you're a hero, and other times it's a way of finding out that you really do need to go back and listen to the original again to make this client happy, but at least you now know where you stand.
The truth that runs through this thread is: "the less of a bass line is already in place the more fun you're going to have." That's why I never object to writing the line w/out even discussing writing credit (I like to work by the hour, baby)...
...smoke 'em out & leave everybody happy, Jimmy. Great question!