I love how the Dies Irae melody, originally a medieval chant, has been universally agreed to represent the concept of death, fate, and judgement day. It is being quoted by many other composers, both classical and modern, and when they do they mean the concept, not just the composition it originated from. When Shostakovich quotes Tchaikovsky's 5th symphony, he refers first to the composition itself, and indirectly to its themes. But Dies Irae is used even in film music, and the medieval origins are hardly relevant. It is a leitmotif unshackled from its original context, open for anyone to use to make the listener feel that doom is imminent.
There's a thematic dictionary for classical paintings, e.g. orange peels represent death. Are there more motives used in music old and new, by different composers in different circumstances, to refer to the same ideas?