A riff is a repeated chord progression or melodic figure, often played by the bass instruments, that forms the basis or an important part of a rock music or jazz composition; an ostinato figure.
Examples of music that depend on riffs for their effect:
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Initially Americans supported Henri Giraud[?], However, at Casablanca conference[?] in June 1943 De Gaulle and Giraud were forced to reconcile and became joint ...