after a pre mastering, can I co it again 3 or 4 times and compare mixes ?
Hi! Busta Speeker here... I believe the only way to COMPARE mixes would be to do a mix, then copy the entire song file-- remember to change the title each time slightly so as to keep track of what's what, i.e. Take1, Take2, etc. Then just play 'em back to back, pick your favorite and delete the rest (or not, you might change your mind)!
Hope this helps; I honestly can't think of another way, short of wasting a CD on ruff mixes-- tho if you don't finalize the disc, you should be able put 'em back to back; that would make critical listening comparisons easier, and MUCH quicker,but it is more work...