On its' own, audio does not need to be synchronised, however when played with video material, more often than not audio will need to be synchronised with video playback, using a timecode reference. For still images, a timecode reference isn't necessary, except where subtitles in the form of lyrics are used.
On one hand, while an Engineer, is most likely concerned, with the day-to-day operations of ensuring things can be heard properly, a Producer on the other hand, is rather more interested with bigger "picture" aspects of sound, including thoughts, feelings and emotions.
Gaining feedback is vital, since taking an existing style and presenting it in a new context, rather than fashioning a genre into a new style; requires experience normally attributable to musicians, however it may also be the role of a Producer.