Such elements include generally short to medium-length songs, written in a basic format (often the verse-chorus structure), as well as the common employment of repeated choruses, melodic tunes, and hooks. Rock music is traditionally built on a foundation of simple unsyncopated rhythms in a 4/4 meter, with a repetitive snare drum back beat on beats two and four. Melodies are often derived from older musical modes, including the Dorian and Mixolydian, as well as major and minor modes. Further fusion subgenres have since emerged, including pop punk, rap rock, and rap metal, as well as conscious attempts to revisit rock's history, including the garage rock/post-punk and synthpop revivals at the beginning of the new millennium. In the 1940s improved microphone design allowed a more intimate singing style and ten or twenty years later inexpensive and more durable 45 r.p.m. Musically, rock has centered on the electric guitar, usually as part of a rock group with electric bass guitar and drums.
By the late 1960s, referred to as the "golden age" or "classic rock" period, a number of distinct rock music subgenres had emerged, including hybrids like blues rock, folk rock, country rock, raga rock, and jazz-rock fusion, many of which contributed to the development of psychedelic rock, which was influenced by the countercultural psychedelic scene. According to Grove Music Online, "Western-derived pop styles, whether coexisting with or marginalizing distinctively local genres, have spread throughout the world and have come to constitute stylistic common denominators in global commercial music cultures". Some non-Western countries, such as Japan, have developed a thriving pop music industry, most of which is devoted to Western-style pop, has for several years has produced a greater quantity of music of everywhere except the USA. The spread of Western-style pop music has been interpreted variously as representing processes of Americanization, homogenization, modernization, creative appropriation, cultural imperialism, and/or a more general process of globalization. Rock music is traditionally built on a foundation of simple unsyncopated rhythms in a 4/4 meter, with a repetitive snare drum back beat on beats two and four. Melodies are often derived from older musical modes, including the Dorian and Mixolydian, as well as major and minor modes.
From about 1967 the term was increasingly used in opposition to the term rock music, a division that gave generic significance to both terms. Whereas rock aspired to authenticity and an expansion of the possibilities of popular music, pop was more commercial, ephemeral and accessible. According to Simon Frith pop music is produced "as a matter of enterprise not art", is "designed to appeal to everyone" and "doesn't come from any particular place or mark off any particular taste". The terms "popular music" and "pop music" are often used interchangeably, although the former is a description of music which is popular (and can include any style). The terms "popular music" and "pop music" are often used interchangeably, although the former is a description of music which is popular (and can include any style). Pop music has been dominated by the American and (from the mid-1960s) British music industries, whose influence has made pop music something of an international monoculture, but most regions and countries have their own form of pop music, sometimes producing local versions of wider trends, and lending them local characteristics. Some of these trends (for example Europop) have had a significant impact of the development of the genre. Rock music is a genre of popular music that originated as "rock and roll" in the United States in the 1950s, and developed into a range of different styles in the 1960s and later, particularly in the United Kingdom and the United States. It has its roots in 1940s' and 1950s' rock and roll, itself heavily influenced by blues, rhythm and blues and country music. Inheriting the folk tradition of the protest song, rock music has been associated with political activism as well as changes in social attitudes to race, sex and drug use, and is often seen as an expression of youth revolt against adult consumerism and conformity. and, in musical terms, it is essentially conservative". From the 1990s alternative rock began to dominate rock music and break through into the mainstream in the form of grunge, Britpop, and indie rock. Harmonies range from the common triad to parallel fourths and fifths and dissonant harmonic progressions. Rock songs, since the late 1950s and particularly from the mid-1960s onwards, often used the verse-chorus structure derived from blues and folk music, but there has been considerable variation from this model. Critics have stressed the eclecticism and stylistic diversity of rock. Because of its complex history and tendency to borrow from other musical and cultural forms, it has been argued that "it is impossible to bind rock music to a rigidly delineated musical definition.