Avant-Prog is short for avant-garde progressive rock. This style appeared in the late 1970s as the extension of two separate prog rock sub-styles: Rock in Opposition (RIO) and prog of the Canterbury scene. The latter, with groups like Egg, Soft Machine, Caravan, and Hatfield & the North (all based in or around the town of Canterbury, England), favored complex compositions bridging classical, rock and jazz idioms, often wrapped in a very British sense of humor that eschewed the typical science-fiction/mystical themes of mainstream prog rock. RIO was a semi-organized movement of the late 1970s regrouping the rock-based avant-garde groups Henry Cow, Etron Fou Leloublan, Univers Zero, Samla Mammas Manna, and Stormy Six.

RIO is a term restricted to temporal limits; Canterbury prog to geographical limits. The late 1970s onward saw the development of an avant-prog scene often functioning in the margin of mainstream prog. A host of groups and artists mainly from the USA, but also from Europe and Japan, started to write mostly short instrumental pieces that focused on complexity and stripped down instrumentation, while avoiding the pomposity and stage props of the big prog acts. Some groups (Thinking Plague and the Motor Totemist Guild, for instance) kept working with epic durations and rich instrumentation but also forayed into free improvisation, sound collage, and other avant-garde techniques. These artists found homes in record labels such as Cuneiform (USA), Recommended (later ReR Megacorp, England) and Rec Rec (Switzerland). Best known groups include Doctor Nerve, Forever Einstein, News from Babel, Miriodor, Boud Deun, Birdsongs of the Mesozoic, and The Muffins. — François Couture

As the name suggests, Experimental Rock is music pushing the envelope of the form, far removed from the classic pop sensibilities of before. Typically, experimental rock is the diametric opposite of standard "verse-chorus-verse" music. Because the whole point is to liberate and innovate, no hard and fast rules apply, but distinguishing characteristics include improvisational performances, avant-garde influences, odd instrumentation, opaque lyrics (or no lyrics at all), strange compositional structures and rhythms, and an underlying rejection of commercial aspirations.

The Neo-Progressive subgenre of progressive rock grew out of a movement in the early 1980s by a number of U.K.-based bands that focused on music that was deeper than new wave, both instrumentally and lyrically. The premier band of the genre was Marillion, who went from lengthy club tours to the top of the charts within a few years and dropped from popular favor almost as fast. Neo-Prog bands are generally influenced by early Genesis, Camel, and to a lesser extent, Van der Graf Generator and Pink Floyd. The music holds a much more lush sound than general rock, but lacks the sophistication of truly symphonic progressive bands like Yes or Camel. Instrumentally, the bands tend to be characterized by a "noodling" approach that focuses on dynamic solos, and at its best, neo-prog lyrics are deep, insightful, and acerbic. Whether neo-prog is diluted progressive or adventurous pop depends on the point of view of the listener -- most progressive rock listeners are likely to find the genre dull and unchallenging, while fans of AOR will find the mix more interesting than most rock bands. Although all of the major bands are still producing albums, the classic era of neo-prog effectively ended when vocalist Fish left Marillion in 1987.

Noise-Rock is an outgrowth of punk rock, specifically the sort of punk that expressed youthful angst and exuberance through the glorious racket of amateurishly played electric guitars. Noise-rock, like its forerunner no wave, aims to be more abrasive, sometimes for comic effect and sometimes to make a statement, but always concentrating on the sheer power of the sound. While most noise-rock bands concentrate on the ear-shattering sounds that can be produced by distorted electric guitars, some also use electronic instrumentation, whether as percussion or to add to the overall cacophony. Some groups are more concerned than others about integrating their sonic explorations into song structures; pioneers Sonic Youth helped bring noise-rock to a wider alternative-rock audience when they began to incorporate melody into their droning sheets of sound. Sonic Youth produced a bevy of imitators, but not all noise-rock resembles their music — '80s bands like the Swans and Big Black took a much darker, more threatening approach, and the Touch & Go label became a center for crazed, shock-oriented takes on the style in the late '80s and '90s. A certain theatrical sub-style of noise-rock, often described as "scuzz-rock" or with similar terms, uses the guitar noise to help create a dirty, decadent, repulsive atmosphere (bands like this include Royal Trux, Pussy Galore, the Dwarves, and the Butthole Surfers

Kraut Rock refers to the legions of German bands of the early '70s that expanded the sonic possibilities of art and progressive rock. Instead of following in the direction of their British and American counterparts, who were moving toward jazz and classical-based compositions and concept albums, the German bands became more mechanical and electronic. Working with early synthesizers and splicing together seemingly unconnected reels of tape, bands like Faust, Can, and Neu created a droning, pulsating sound that owed more to the avant garde than to rock & roll. Although the bands didn't make much of an impact while they were active in the '70s, their music anticipated much post-punk of the early '80s, particularly industrial rock. Kraut rock also came into vogue in the '90s, when groups like Stereolab and Tortoise began incorporating the hypnotic rhythms and electronic experiments of the German art-rock bands into their own, vaguely avant-garde indie rock

Progressive rock and art rock are two almost interchangeable terms describing a mostly British attempt to elevate rock music to new levels of artistic credibility. The differences between prog-rock and art rock are often slight in practice, but do exist. Prog-rock tends to be more traditionally melodic (even when multi-sectioned compositions replace normal song structures), more literary (poetry or sci-fi/fantasy novels), and more oriented toward classically trained instrumental technique (with the exception of Pink Floyd). Art rock is more likely to have experimental or avant-garde influences, placing novel sonic texture above prog-rock's symphonic ambitions. Both styles are intrinsically album-based, taking advantage of the format's capacity for longer, more complex compositions and extended instrumental explorations. In fact, many prog bands were fond of crafting concept albums that made unified statements, usually telling an epic story or tackling a grand overarching theme. In addition to pushing rock's technical and compositional boundaries, prog-rock was also arguably the first arena where synthesizers and electronic textures became indispensable parts of a rock ensemble. The earliest rumblings of progressive and art rock could be heard in the poetry of Bob Dylan and conceptually unified albums like the Mothers of Invention's Freak Out! and the Beatles' Sgt. Pepper's Lonely Hearts Club Band, all of which suggested that rock was more than just teenagers' music and should be taken seriously as an art form. Prog-rock began to emerge out of the British psychedelic scene in 1967, specifically a strain of classical/symphonic rock led by the Nice, Procol Harum, and the Moody Blues (Days of Future Passed). King Crimson's 1969 debut In the Court of the Crimson King firmly established the concept of progressive rock, and a quirky, eclectic scene was taking shape in Canterbury, led by the jazzy psychedelia of the Soft Machine. Prog-rock became a commercial force in the early '70s, with Emerson, Lake & Palmer, Yes, Jethro Tull, Genesis, and Pink Floyd leading the way. Meanwhile, a more avant-garde scene (dubbed Kraut-rock) was developing in Germany, and eccentric, unclassifiable bands continued to emerge in the U.K. By the mid-'70s, a backlash was beginning to set in; prog-rock sometimes mistook bombast for majesty, and its far-reaching ambition and concern with artistic legitimacy could make for overblown, pretentious music. Its heyday soon came to an end with the advent of punk, which explicitly repudiated prog's excesses and aimed to return rock & roll to its immediate, visceral roots. Still, prog-rock didn't completely go away. A number of AOR bands used prog ideas in more concise songs; plus, Pink Floyd, Yes, and Genesis all had number one singles in the '80s by retooling their approaches. A small cult of neo-prog bands catered to faithful audiences who still liked grandiose concepts and flashy technique; the first was Marillion, and many more popped up in the late '80s and early '90s