political activism. Frith also said the main purpose of pop music is to create revenue. It is not a medium of free articulation of the people. Instead, pop music seeks to supply the nature of personal desire and achieve the instant empathy with cliche personalities, stereotypes, and melodrama that appeals to listeners. It is mostly about how much revenue pop music makes for record companies. Music scholar Timothy Warner said pop music typically has an emphasis on recording, production, and technology, rather than live performance; a tendency to reflect existing trends rather than progressive developments; and seeks to encourage dancing or uses dance-oriented rhythms. The main medium of pop music is the song, often between two and a half and three and a half minutes in length, generally marked by a consistent and noticeable rhythmic element, a mainstream style and a simple traditional structure. The structure of many popular songs is that of a verse and a chorus, the chorus serving as the portion of the track that is designed to stick in the ear through simple repetition both musically and lyrically. The chorus is often where the music builds towards and is often preceded by "the drop" where the bass and drum parts "drop out". Common variants include the verse-chorus form and the thirty-two-bar form, with a focus on melodies and catchy hooks, and a chorus that contrasts melodically, rhythmically and harmonically with the verse. The beat and the melodies tend to be simple, with limited harmonic accompaniment. The lyrics of modern pop songs typically focus on simple themes – often love and romantic relationships – although there are notable exceptions. Harmony and chord progressions in pop music are often "that of classical European tonality, only more simple-minded." Clichés include the barbershop quartet-style harmony (i.e. ii – V – I) and blues scale-influenced harmony. There was a lessening of the influence of traditional views of the circle of fifths between the mid-1950s and the late 1970s, including less predominance for the dominant function. Development and influence Technology and media In the 1940s, improved microphone design allowed a more intimate singing style and, ten or twenty years later, inexpensive and more durable 45 rpm records for singles "revolutionized the manner in which pop has been disseminated", which helped to move pop music to "a record/radio/film star system". Another technological change was the widespread availability of television in the 1950s with