Musical characteristics
Form:
Progressive rock songs either avoid common popular music song structures of verse-chorus-bridge, or blur the formal distinctions by extending sections or inserting musical interludes, often with exaggerated dynamics to heighten contrast between sections. Classical forms are often inserted or substituted, sometimes yielding entire suites, building on the traditional medleys of earlier rock bands. Progressive rock songs also often have extended instrumental passages, marrying the classical solo tradition with the improvisational traditions of jazz and psychedelic rock. All of these tend to add length to progressive rock songs, which may last longer than twenty minutes.
Timbre (instrumentation and tone color):
Timbre (instrumentation and tone color):
Early progressive rock groups expanded the timbral palette of the then-traditional rock instrumentation of guitar, organ, bass, and drums by adding instruments more typical of jazz or folk music, such as flute, saxophone and violin, and more often than not used electronic keyboards, synthesizers, and electronic effects units. Some instruments – most notably the Moog synthesizer and the Mellotron – have become closely associated with the genre.
Rhythm:
Drawing on their classical, jazz, folk and experimental influences, progressive rock artists are more likely to explore time signatures other than 4/4 and tempo changes. Progressive rock generally tends to be freer in its rhythmic approach than other forms of rock music. The approach taken varies, depending on the band, but may range from regular beats to irregular or complex time signatures.
Melody and Harmony:
In prog rock, the blues inflections of mainstream rock are often supplanted by jazz and classical influences. Melodies are more likely to be modal than based on the pentatonic scale, and are more likely to comprise longer, developing passages than short, catchy ones. Chords and chord progressions may be augmented with 6ths, 7ths, 9ths, and compound intervals; and the I-IV-V progression is much less common. Allusions to, or even direct quotes from, well-known classical themes are common. Some bands have used atonal or dissonant harmonies, and a few have even worked with rudimentary serialism.
Texture and imagery:
Ambient soundscapes and theatrical elements may be used to describe scenes, events or other aspects of the concept. For example, Leitmotif is used to represent the various characters in Genesis' "Harold the Barrel" and "Robbery, Assault and Battery." More literally, the sounds of clocks and cash registers are used to represent time and money in Pink Floyd's The Dark Side of the Moon.
Technology:
To aid timbral exploration, progressive rock bands were often early adopters of new electronic musical instruments and technologies. The analog synthesizer is the instrument best associated with progressive rock. This included the modular Moog used by ELP, Mini Moog by Yes, ARP Pro Soloist by Genesis, Oberheim by Styx, etc. The mellotron, particularly, was a signature sound of early progressive bands. Pink Floyd utilized an EMS Synthi A synthesizer equipped with a sequencer on their track "On the Run" from their 1973 album Dark Side of the Moon. In the late 1970s, Robert Fripp, of King Crimson, and Brian Eno developed an analog tape loops effect (Frippertronics). In the 1980s, Frank Zappa used the Synclavier for composing and recording, and King Crimson utilized MIDI-enabled guitars, a Chapman Stick, and electronic percussion.
Concept albums:
Collections of songs unified by an elaborate, overarching theme or story are common to progressive rock. As songs by progressive rock acts tend to be quite long, such collections have frequently exceeded the maximum length of recorded media, resulting in packages that require multiple vinyl discs, cassettes, or compact discs in order to present a single album. Concepts have included the historical, fantastical, and metaphysical, and even, in the case of Jethro Tull's Thick as a Brick, poking fun at concept albums.
Lyrical themes:
Progressive rock typically has lyrical ambition similar to its musical ambition, tending to avoid typical rock/pop subjects such as love, dancing, etc., rather inclining towards the kinds of themes found in classical literature, fantasy, folklore, social commentary or all of these. Peter Gabriel (Genesis) often wrote surreal stories to base his lyrics around, sometimes including theatrical elements with several characters, while Roger Waters (Pink Floyd) combined social criticism with personal struggles with greed, madness, and death.
Presentation:
Album art and packaging is often an important part of the artistic concept. This trend can be seen to have begun with The Beatles' Sgt. Pepper's Lonely Hearts Club Band and played a major part in the marketing of progressive rock. Some bands became as well known for the art direction of their albums as for their sound, with the "look" integrated into the band's overall musical identity. This led to fame for particular artists and design studios, most notably Roger Dean for his work with Yes, and Hipgnosis for their work with Pink Floyd and several other progressive rock groups.
Stage theatrics:
Beginning in the early 1970s, some progressive rock bands began incorporating elaborate and sometimes flamboyant stage theatrics into their concerts. Genesis lead singer Peter Gabriel wore many different colourful and exotic costumes in one show and frequently acted out the lyrical narrative of the songs, Yes incorporated futuristic stage sets designed by Roger Dean, performing 'in-the-round', and one of ELP's many stage antics include Emerson's "flying piano" at the California Jam concert, in which a Steinway grand piano would be spun from a hoist.
