Doo-wop is a style of vocal-based rhythm and blues music developed in African American communities in the 1940s, achieving mainstream popularity in the 1950s and early 1960s. It emerged from New York City, Philadelphia, Chicago, Baltimore, Newark, New Jersey, Pittsburgh, Cincinnati, Detroit, Washington, D.C., and areas of greater Los Angeles, including El Monte and Compton. Built upon vocal harmony, doo-wop was one of the most mainstream, pop-oriented R&B styles of the time. Singer Bill Kenny is often noted as the "Godfather of Doo-wop" for his introduction of the "top & bottom" format used by many doo-wop groups. This format features a high tenor lead with a "talking bass" in the song's middle. As a musical genre, doo-wop features vocal group harmony with the musical qualities of many vocal parts, nonsense syllables, a simple beat, sometimes little or no instrumentation, and simple music and lyrics. It is ensemble single artists appearing with a backing group. Solo billing usually implies an individual is more prominent in the musical arrangement.