Something very thought provoking, which I hope will assist in some heavy media sorting once I really start giving the "omnimedia" key focus the shake-down. It's Marshall McLuhans' tetrad, and it is used in this way (paraphrase from Wiki)
• Enhancement (figure): What the medium amplifies or intensifies. For example, radio amplifies news and music via sound.
• Obsolescence (ground): What the medium drives out of prominence. Radio reduces the importance of print and the visual.
• Retrieval (figure): What the medium recovers which was previously lost. Radio returns the spoken word to the forefront.
• Reversal (ground): What the medium does when pushed to its limits. Acoustic radio flips into audio-visual tv.