Popular music and the music that enjoys popularity are not necessarily the same thing. Although there has been great improvement in the content of pop music since the mid-1950s, there is still a lot of trivia produced for consumption by 1968's adolescent Babbits.

This admixture of quality and pap hurls a real challenge to the record-buyer, the disk-jockey, and the ticket-buyer. If one lets his critical guard down for minute, the promoters can storm across the threshold. How else can one explain the triumphs of Paul Mauriat and his Tchaikovskyesque Muzak? How else could "Hair" cause boredom among the knowledgeably sophisticated of all ages and still excite dithyrambs from the ambience-chasers who would have walked out on a performance of The Fugs a few months earlier? The list is regrettably long. One could even add to them those slick artisans Simon and Garfunkle who are becoming increasingly like that thin and bashful photographer on the beach - underdeveloped and overexposed.

We are predictably entering a new era in which the challenging cynicism that American youth has exercised toward all Establishment products and lifestyles will be turned toward the popular culture scene. When that day arrives, "Hair" will get trimmed and The Fugs will be philosopher-kings. The musical show has simply borrowed the external trappings of The Fugs' super hippie outrages at convention and dull normality and turned it into a commercially acceptable cliché of musical and social inconsequence.

The work of The Fugs is by no means of an even consistency. Heaven help the protest poets if they ever do get to be polished. But their latest album, Tenderness Junction (Reprise 6280), is their most musical work yet. After some false starts on Broadside and ESP, the Fugs are ready to do battle in the commercial marketplace with their anti-commercial rants, their satirical slashes that draw blood, their Lenny Bruce-isms that hit the conventional middle-class right between its myopic, suburban eyes. The contrast and comparison between "Hair" and The Fugs could make a long article but this is a record column merely calling attention to the sextet's hymnology to an American cultural revolution on its best album yet.

The new lease on life obtained by The Fugs in recording for a West Coast label that has been causing a stir in music circles, call attention to some other second-time-around artists who Reprise is giving excellent productions when others thought they were no longer commercially viable. Jack Elliott, that bedrock city folknik who filled the gap between the generations of Woody Guthrie and Patrick Skye has a lustrous and illustrious album on Ramblin' Jack Elliott's Brigham (Reprise 6284). He has made at least 20 albums, including many a gem, but this is one of his best. Bruce Langhorne produced this LP under executive producer Andy Wickham in an album that rings as much with tradition as it does with modernity, dualism that used to undo certain folk fans. The Elliott album ranges from an experimental quasi-raga "If I Were a Carpenter," to a folkish "Goodnight Little Arlo," a song to a colleague also recording for Reprise. With this kind of singing and this kind of recording, Jack Elliott will never go out of style.

A few words of praise are in order for Reprise and its new orientation. It is no blanket plug for a record company to call for public attention to the meritorious releases of the label, past, present and for the immediate future. Coming, for example, is an album by a discovery of Bob Dylan's, named Sir Douglas, who has been described as a male Janis Joplin. Already recorded are two new song-writers, Randy Newman and Joni Mitchell, who are complex, artful and imaginative trend-setters.

A considerable stripe above most contemporary folk-pop song-writing can be heard on Joni Mitchell (Reprise 6293) and Randy Newman (Reprise 6286). Thanks to previous recordings of Miss Mitchell's work by Judy Collins and Dave Van Ronk, Miss Mitchell has already become an underground rage. She has a delicate pen, dipped in evanescent imagery never far from comprehension, but tickling to the senses and the intellect.

He singing has a haunting song-off-the-moors quality that should further help to establish her reputation.

Mr. Newman is a droll and cunning song-writer with a style vaguely reminiscent of Hoagy Carmichael's, in which he smears phrases as if finger painting. But Mr. Newman, to continue the art images, is a sort of Jacob Epstein of Silly Putty, building most intriguing statuary. He's had a big influence on the English singer Alan Price and the word from London is that the Beatle's' "When I'm Sixty-Four" was heavily influenced by Randy Newman's style.

There are several other Reprise or sister Warners label albums worth hearing. Two New York singers and song-writers who found the West Coast climate freer and more rejuvenative are heard on Hamilton Camp - Here's To You (Warners-Seven Arts 1737) and David Blue: These 23 Days in September (Reprise 6296). Messrs. Camp and Blue posit two unresolved answers to manners of personal style, the former compensating with extroversion while the latter is slowly coming out of a defensive introversion. Both are given beautiful production assistance on these albums, and both stand for earnest talent that may not set the world afire, but does kindle small flames to brighten the landscape.

The Top Ten of the trade paper hit charts may never see the work of The Fugs, Jack Elliott, Sir Douglas, Joni Mitchell, Randy Newman, Hamilton Camp or Dave Blue. "Chart action" as they call it, is still no index to artistry or quality. But I wish them and Reprise well because there are high standards at work here that merit popular and commercial success. The historic album for Reprise by Van Dyke Parks previously discussed in these columns by Richard Goldstein is an artistic triumph that cost $50,000 to produce and has yet to sell 10,000 copies. It is like the old days of classical recordings. The imperative message to the pop-record buyer is: support quality or it will disappear, or sell out to the promoters.