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:
... travels of Martin Gerritz de Vries[?] in the 17th century, and still better from those of La Pérouse (1787) and Krusenstern (1805). Both, however, regarded it as a ...