Medium of production is basically just the same as medium.
The most salient point is that different mediums work in different ways. An image, for example, works visually, while a poem works with words. Film uses audio (including music, dialogue), visual (effects, shot choice), as well as incorporating other forms (e.g. the written prologues of the Star Wars films).
So your job is to explore how the use of different mediums affects the messages in each text. Best way of thinking about this is by looking at adaptations: for example, how does a film like Minority Report make us think and feel differently to Philip K Dick's original short story? The issue is not which is better, but the technical mechanisms through which each does different things. The Tom Cruise film uses camera angles and cutting really well to create suspense and tension, for example, while Dick's short story is very sparse and dialogue-based - which, in my opinion, lends more to an exploration of the philosophical issues of causality.
Instead of thinking of texts as just "naturally" of one medium or another, you want to end up contemplating why and how a composer has used a specific medium for their work.