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