Micro editing like being able to raise let's say the volume of that "D" note of the midi bass guitar on the 4th beat of measure 24
Or let's say make that note a 1/4 note instead of an 1/8 note
Or maybe Tweak the EQ of the midi snare drum perhaps add a bit of highs
Or add reverb to just the snare drum, not the entire drum kit
That sort of stuff