Conversation so far:
What is notable about The Beatles's music style?
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His melody lines are characterised as primarily "vertical", employing wide, consonant intervals which express his "extrovert energy and optimism".
Are there any other interesting aspects about this article?
the Fab Four revolutionised the sound, style, and attitude of popular music and opened rock and roll's doors to a tidal wave of British rock acts.

Question: What is the Fab Four?
Self-contained rewrite: What is the Fab Four?