Sound
Separation
Also called instrument separation
Separation is how clearly individual instruments and voices stay distinct when they play at once. Poor separation turns a busy chorus into a wall of sound; good separation lets you follow one part through it.
Separation depends on low distortion, control in the bass so it does not mask the mids, and a tuning that does not pile energy into one region. Dense rock and big-band recordings show it quickly.
It is related to Imaging, which is about where each sound sits, and to Resolution, which is about how much detail is heard. A product can image well and still smear instruments that share the same space.