An example of commenting on a scene would be having sad music under sad dialog, or effusively heroic music under a heroic action scene, or comedic music accompanying physical comedy (slapstick, etc.). In the early days of film this was a very typical way of scoring movies – the music essentially mirrored what was on the screen. Today that approach tends to be avoided and seen as old-fashioned. I believe it was the great Jerry Goldsmith who once said “Don’t’ score the man running, score WHY he’s running.”
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