Pitch rise effect and loop recording at a later date

[phillyt2k]

Sorry for all the threads but i need your knowledge again. I've squashed 2 questions into one.

Firstly creating a dramtic pitch bend effect. I have a signal generator with a sawtooth wave on it. I am automating the frequency from 20Hz to 2kHz. I have a gradual line (using the line tool). I notice that the pitch doesnt rise uniformly, it does up until about 1300Hz, then it seems to rise at a faster rate if that makes sense? So I am having to make the line less steep to wards the end to try and counteract this. I'm thinking maybe it should be a parabolic curve or something instead. Yet I can't draw this in.

My second problem is loop recording at a later date.

I have recorded a four bar part. If I want to go back to it at a later date and record the same four bar part but still keep it as part of the playlist how can I do this?

Using loop record just records over the original.Is there anyway to keep the original recording. Basically I want to be able to do normal loop recording, but like over a longer period of time if that makes sense, so record take 1 on monday, take 2 on tuesday, take 3 wednesday etc, but still have them all in the same playlist. Is this possible?