In the case of 2 or 3 solo string parts playing in unison and in a fast movement how can I avoid getting that annoying sound, not sure how to describe it though, but it's not the natural timbre of the instrument anymore...Phase problem or something...? And why doesn't this happen with live instruments? Or does it?
Is it the same solo instrument? If so then you are getting phasing because the same samples are playing against each other. In the "real" world nobody is playing on the same instrument so it doesn't happen. FWIW I did an overdub session where the cellist was multitracking and was so accurate he was seriously phasing with himself.......!
DG