producer - tells band what to do, how to play, how to sing, ("i want you to EMPHASISE the word "HATE", i want to really FEEL how you HATE the world... let it all out man") organizes the recording session and occasionally fucks around with arrangement
sound engineer - places mics, records instruments, presses buttons on mixing console, spills coffee over mixing console etc
art director - some pretentious asshat who sits around with photoshop thinking long and hard about whether franklin gothic lt or franklin gothic lt condensed would fit the "mood" of the album better
mixing engineer - mixes the tracks recorded by the sound engineer (in co-op with the producer) at tracking stage. setting levels, also eq adjustments & effects are added at mix stage