Doo-wop is a genre of music that was developed in African-American communities in The USA. It started in the 1940s. Doo-wop achieved mainstream popularity in the 1950s and early 1960s. Built upon vocal harmony, doo-wop was one of the most mainstream, pop-oriented R&B styles of the time. Singer Bill Kenny (1914–1978) is often called the "Godfather of Doo-wop". He introduced the "top and bottom" format which featured a high tenor singing the lead and a bass singer reciting the lyrics in the middle of the song. Doo-wop features vocal group harmony, nonsense syllables, a simple beat, sometimes little or no instrumentation, and simple music and lyrics.