Soundwise
I see. Any macro to morph between different strings?
If you mean switch to different strings when playing to trigger the
same notes on
different strings, that's not really what macros are all about - they connect modulation sources and destinations. There
is key switching and velocity switching, but what that won't do is randomized or round-robin switching, i.e., you can play the exact same note with the exact same velocity and trigger a different sample. There probably is a way to do that with multiple instances of Rapture Pro, but figuring it out would likely make my head explode.
However, I tend to use the synthesis elements to add variety. For example, instead of switching among samples with different velocities - which often sounds "fake" to me - I prefer to sample a string that's hit fairly hard, and then tie velocity to filter cutoff so that hitting the key harder makes for a brighter sound. I also tie it inversely to sample start time, so hard-hit notes catch more of the sample's beginning and softer notes begin further into the sample to reduce the pick or finger hit. Because these are nice, linear functions instead of switching, they sound more natural to me.
Then again when I want to play bass, I play bass
Because I also double on keyboards, I want a keyboard bass to react more like a cross between the sonically organic vibe of a real bass, and a playing style that's more congruent with keyboards. On my new album, most of the parts are keyboard bass as they complement the "real" drums, guitars, and vocals well.
Is it possible at all to use macros to morph between different elements?
Yes, you can crossfade between different elements although the Vector mixer feature sounds more like what you want. I also do wave sequencing with Rapture Pro, i.e., audio files trigger sequentially and crossfade into one another to produce a continually evolving timbre.