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:
... with 27.6% under the age of 18, 6.2% from 18 to 24, 17.7% from 25 to 44, 36.0% from 45 to 64, and 12.5% who are 65 years of age or older. The median age is 44 years. For ...