From “The Rolling Stone Record Guide” published by Random House/Rolling Stone Press in 1979
Cajun: Literally, Louisianans of French-Canadian descent. The term is a corruption of "Acadian"; French Canada was known as Acadia until the British conquest, when many French-Canadian settlers moved themselves to settle in Louisiana, which was a French colony until Jefferson bought it from Napoleon. Cajuns have retained their cultural identity, and their version of rock & roll has many French-and some black-elements. (When performed by blacks, Cajun music is known as zydeco, an offshoot of the blues popularized recently by the accordionist Clifton Chenier.) Cajun music is sung in a French-American patois that’s unintelligible to the uninitiated; its accents tend to be lilting and sonorous. Doug Kershaw is a Cajun, although he doesn’t play Cajun music any more. 
Chicago Blues: Chicago blues is a direct outgrowth of delta blues. It was chiefly developed after World War II by musicians from the delta regions of Mississippi, Louisiana and Arkansas who came north for jobs during the war years. It is both an attempt to retain some sense of rural tradition and a response by people steeped in that tradition to their encounters with urban living. While Chicago blues kept some stylistic elements of delta blues, it discarded and deemphasized others. While the resulting form is less lyrical, it is more powerful, accenting heavy beat, incorporating drums and electric guitars and bass. The chief difference between Chicago and delta styles is that the former is band music, usually including guitar, bass, drums, harmonica and/or piano, and the latter is solo- or duo-oriented. Key Chicago bluesmen include Muddy Waters, Howlin’ Wolf, both Sonny Boy Williamsons and Little Walter, among a host of others. The influence of Chicago blues on modern rock has been enormous, indicated by the fact that the current rock group lineup is derived from the basic Chicago setup.
Concept Album: Literally, any album unified by a theme, whether instrumental, compositional, narrative or lyric. Most often, the latter applies, though some of the most famous concept albums-especially the Beatles’ Sgt. Pepper’s Lonely Hearts Club Band are linked by a concept that is exclusively musical. Pete Townshend‘s extended narrative works Tommy and Quadrophenia, the so-called rock operas, are certainly concept albums, but no more so than The Who Sell Out, in which the songs are not narratively tied together but the tracks are unified by inserting radio commercial parodies between them. And, at least arguably, The Who by Numbers is a concept album, linked together by Townshend’s continual brooding on the plight of the aging rockers. This does not mean that an album of love 
songs is necessarily a concept album, however; some overriding and self-conscious attempt to link such songs together is usually implied. It is fair to say, however, that most "classic" rock albums since Sgt. Pepper are unified in some such fashion and that the LP-as-art-form is inevitably conceptual.
Cool: Jazz idiom devised on West Coast in Fifties, notable for a much softer approach than the dominant jazz of the time, bop. Cool was developed principally by white, college-educated musicians, and never was very "cool" (in the slang sense) among jazz insiders on the East Coast. The great exception, though, was Miles Davis, who made some exquisite recordings in the style in the early Fifties experimentation.
Country: More specifically, country & western, but generally abbreviated to just the former. Country is the music of rural Southern and Southwestern America, arguably founded by the late-Twenties recordings of the Carter Family and Jimmie Rodgers. It bears some relationship to blues the repertoire shares common folk antecedents, and certain musical elements are common to both-but country tends to be a music of resignation (particularly social resignation) rather than the release that is the staple of blues. In the last twenty years, country has become an appendage of pop and has lost much of its stylistic identity in the process of homogenization.
Country Rock: Hybrid of rock beat and country accents. Rockabilly, the style of rock & roll Elvis Presley sang-had specific country elements, but country rock was really founded as a-hybrid genre in the late Sixties by such albums as the Byrds’ Sweetheart of the Rodeo, Sometimes the reference is as much to visual style-long hair and so forth-as to sound: the background of the performers also plays a part. The Flying Burrito Brothers, in Gram Parsons’ tenure with them, played almost straight country music, but the hirsute band members, some of whom had rock bands in the shadows of their past, made it a countryrock group. Generally, as with most hypenated rock forms, country rock has not been terribly successful artistically; the Burritos and the later incarnations of the Byrds were probably the best at it, although by now nearly everyone from the Beatles and Rolling Stones to Elvis Costello and Bruce Springsteen has written or performed some country-rock material.
Cover Versions: A cover version is, broadly, any recording of a song by a performer other than the original or a version of a song performed by a singer other than the writer. Linda Ronstadt is a cover artist because she does not write her own material, her Buddy Holly interpretations are covers, regardless of whether Holly wrote the songs. More narrowly, a cover is a carbon copy of another’s performance, a practice that 
was rampant in the Fifties, when white singers (Pat Boone, the Crew-Cuts, etc.) made exact imitations of R&B hits for the white market, thereby usurping sales and airplay of the originals. In the Fifties, this generally meant taking the overt sexuality out of song, though not all covers crossed racial or stylistic lines: Elvis Presley covered Carl Perkins’ original of "Blue Suede Shoes," for instance, without emasculating it. The latter kind of cover is still a common practice in reggae and European pop; the last major cover version in America was Stories‘ cover of "Brother Louie," originally done by the biracial English group Hot Chocolate.
Delta Blues: Blues from the Mississippi River delta region which stretches from just south of Memphis to northern Louisiana and takes in the principal cottoning areas of Mississippi and Arkansas. Many of the greatest bluesmen- Robert Johnson, Charley Patton, Muddy Waters, Howlin’ Wolf, Son House, both Sonny Boy Williarnsons – were of delta origin. In part the notion of blues as a music of oppression comes from its association with this region which is probably the most racist in America. However delta blues has a wide emotional range and in the hands of a master like Mississippi John Hurt for instance can move from liltingly lyrical dance tunes to bad-man ballads. All rural blues is not delta blues although the greatest rural blues did emerge from the delta.
Demo: A tape or disc made for demonstration purposes. as when a songwriter makes a skeletal arrangement of his tune in hopes of attracting a singer to it. Sometimes such a tape or record when made by a performer in hopes of obtaining a recording contract.
Detroit Sound: 1. In R&B and soul. Motown’s sound which fused adult black music with teenage concerns and became a dominant Sixties pop expression. 2 In rock the later hard rock of such groups as MCS. the Stooges, Grand Funk Railroad and Ted Nugent. The hard rock of Detroit played a major role in shaping both punk and heavy metal. with its heavy emphasis on industralized beat and walls of electronic sound.
Disco: An abbreviation of the word discotheque. The term refers either to a dance hall (discos enjoyed a brief pre-Beatles Sixties vogue. when the Twist was the rage) or in the Seventies to records designed to be played in discotheques, A dominant pop form in the late Seventies.
Dixieland: Name given to the New Orleans jazz style of pre-World War I vintage but applies only to its later embellishments and (mostly) corruptions not to real "hot jazz" itself.
Doo-Wop: Term applied to a style of black R&B vocal groups in the Fifties who often based their harmonies around simple repeated phrases like "doo-wop". The term does not properly apply to any nonsense syllable singing but only to the kind of ornately arranged vocal choruses popularized by the so-called street-corner groups. who worked out their moody sounds on the street corners of New York. Philadelphia, etc. Classic doo-wop singles include "Gee" by the Crows. "Sh-Boom" by the Chords and the Penguins‘ "Earth Angel."
Retrorambling 
Love this article and the C-D glossary. Totally agree that Dance, Trance, etc. are irrelevant to me.
It’s a good thing the old stuff is still alive 🙂