In a broad sense, pop is any music based on memorable melodies, repeated sections (usually, but not always, verses and choruses), and a tight, concise structure that keeps the listener's focus on those elements. Pop as a musical style, however, began in the late '90s and early 2000s, when a pair of major forces began narrowing and focusing commercial tastes. First, the heavy influence of rap and R&B made the pop singles charts more homogeneous than ever. Then, the advent of the television contest American Idol further centralized what people agreed on as pop music. As such, Pop is primarily influenced by the time's two most broadly popular styles: R&B and adult contemporary. The sound of Backstreet Boys and Britney Spears in the mid-to-late '90s was of prime importance to the genesis of Pop, as were R&B superstars Aaliyah and R. Kelly, both of whom had a heavy adult contemporary angle to their material. By the 2000s, a parade of varying artists were catering to the mainstream with a similar type of pop music - artists as diverse as Destiny's Child, Black Eyed Peas, Faith Hill, Maroon 5, Keith Urban, and AmIdol alums like Kelly Clarkson and Clay Aiken. Not everything they recorded was Pop, but in varying degrees they included several bids to the mainstream each year and on each album. Although the essentials of songcraft were still much in abundance, their songs were as much about production as performance.