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:
... urethra is a tube that connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes, to pass urine to the outside, and also ...