A good definition of rock, in fact, is that it's popular music that to a certain degree doesn't care if it's popular.
—Bill Wyman in Vulture (2016)
Red Hot Chili Peppers
in 2006, showing a quartet lineup for a rock band (from left to right: bassist, lead vocalist, drummer, and guitarist).
The sound of rock is traditionally centered on the amplified electric guitar, which emerged in its modern form in the 1950s with the popularity of rock and roll. Also, it was influenced by the sounds of electric blues guitarists. The sound of an electric guitar in rock music is typically supported by an electric bass guitar, which pioneered in jazz music in the same era, and percussion produced from a drum kit that combines drums and cymbals. This trio of instruments has often been complemented by the inclusion of other instruments, particularly keyboards such as the piano, the Hammond organ, and the synthesizer. The basic rock instrumentation was derived from the basic blues band instrumentation (prominent lead guitar, second chordal instrument, bass, and drums). A group of musicians performing rock music is termed as a rock band or a rock group. Furthermore, it typically consists of between three (the power trio) and five members. Classically, a rock band takes the form of a quartet whose members cover one or more roles, including vocalist, lead guitarist, rhythm guitarist, bass guitarist, drummer, and often keyboard player or other instrumentalist.
A simple 4/4 drum pattern common in rock music Play (help
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 often originate from older musical modes such as the Dorian and Mixolydian, as well as major and minor modes. Harmonies range from the common triad to parallel perfect fourths and fifths and dissonant harmonic progressions. Since the late 1950s and particularly from the mid 1960s onwards, rock music 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 its 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."
Unlike many earlier styles of popular music, rock lyrics have dealt with a wide range of themes, including romantic love, sex, rebellion against "The Establishment", social concerns, and life styles. These themes were inherited from a variety of sources such as the Tin Pan Alley pop tradition, folk music, and rhythm and blues. Music journalist Robert Christgau characterizes rock lyrics as a "cool medium" with simple diction and repeated refrains, and asserts that rock's primary "function" "pertains to music, or, more generally, noise." The predominance of white, male, and often middle class musicians in rock music has often been noted, and rock has been seen as an appropriation of black musical forms for a young, white and largely male audience. As a result, it has also been seen to articulate the concerns of this group in both style and lyrics. Christgau, writing in 1972, said in spite of some exceptions, "rock and roll usually implies an identification of male sexuality and aggression".
Since the term "rock" started being used in preference to "rock and roll" from the late-1960s, it has usually been contrasted with pop music, with which it has shared many characteristics, but from which it is often distanced by an emphasis on musicianship, live performance, and a focus on serious and progressive themes as part of an ideology of authenticity that is frequently combined with an awareness of the genre's history and development. According to Simon Frith, rock was "something more than pop, something more than rock and roll" and "[r]ock musicians combined an emphasis on skill and technique with the romantic concept of art as artistic expression, original and sincere".
In the new millennium, the term rock has occasionally been used as a blanket term including forms like pop music, reggae music, soul music, and even hip hop, which it has been influenced with but often contrasted through much of its history. Christgau has used the term broadly to refer to popular and semipopular music that cater to his sensibility as "a rock-and-roller", including a fondness for a good beat, a meaningful lyric with some wit, and the theme of youth, which holds an "eternal attraction" so objective "that all youth music partakes of sociology and the field report." Writing in Christgau's Record Guide: The '80s (1990), he said this sensibility is evident in the music of folk singer-songwriter Michelle Shocked, rapper LL Cool J, and synth-pop duo Pet Shop Boys—"all kids working out their identities"—as much as it is in the music of Chuck Berry, the Ramones, and the Replacements.