Thematic scores (think Raiders of the Lost Ark, Spider-Man, Bond movies) use distinct and recognizable themes and/or motifs to help tell the story. Atmospheric scores avoid strong memorable themes (they may still use motifs, but not as much if at all) but are more ambient and moody (think Gravity, Blade Runner, The Social Network, and so many horror films). Neither is better than the other, it’s a stylistic choice.
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