Heavy metal is conventionally featured by emphatic rhythms, loud distorted guitars, vigorous vocals and dense bass-and-drum sound. Metal subgroups variously alter, emphasize, or omit one or more of these features. New York Times detractor Jon Pareles writes, "In the taxonomy of popular music, heavy metal is a major subspecies of hard-rock—the breed with less syncopation, less blues, more showmanship and more brute force." The normal band lineup encompasses a drummer, a rhythm guitarist, a bassist, a singer and a lead guitarist. Keyboard instruments are sometimes used to improve the fullness of the sound.