Ry Cooder deserves attention for many reasons, but one is particular stands out. No other popular musician has made so much use of our populist musical heritage and certainly no one has done so much to make people aware of this country's ethnic flavors. His last album, "Chicken Skin Music" (Reprise MS 2254) assimilated two different but complementary regional styles, Hawaiian and Tex-Mex.

The album's title, incidentally, is derived from a Hawaiian expression for "something that gives goose bumps," and Cooder's imaginative incorporation of two legendary players, accordionist Flaco Jimenez and slack-key and steel guitarist Gabby Pahinui, allow the album to live up to its name.

Cooder's commitment is total. Before meeting Jimenez, he spent six months learning one of the accordionist's most difficult songs note for note. Jimenez not only responded by appearing on "Chicken Skin Music" but spent six months on the road with Cooder last hear, his first extended leave from the border area of Texas and Mexico.

Jimenez' exuberant vitality is but one of the treats which can be heard on Cooder's new album. "Show Time" (Warner Brothered BS 3059), a live recording that brilliantly captures not only Cooder's exquisite botteneck guitar and mandolin work, but his love for regional and ethnic music.

For instance, Pahinui could be a part of the Chicken Skin Revue, so another flavor was added in the form of three dynamic black gospel singers: Eldridge King, Terry Evans and Bobby King.Cooder's inituitive feel for gospel is evident on the traditional "Jesus Is on the Mainline," which has just enough rough edges attesting to its authenticity and which is marked by some stunning bottleneck work.

All three singers take a turn on Dan Penn's haunting "Dark End of the Street," with Cooder laying down some basic Pops Staples electric guitar to goad the singers into ecstatic emoting that evokes fond memories of Sam Cooke and Al Green at their most sensual.

Cooder's voice has become more assured over the years; and in all his instrumental work, too, he continues to display remarkable restraint. He says more by saying less: subtleties of spacing, intervals and rhythmic manipulation mark his unique and personal style.

Flaco Jimenez is featured on several cuts on the new album: "Viva Sequin/Do Re Mi" and Volver, Volver." He is a major representative of "musica norteno," a style which developed around the turn of the century in the South Texas/Northern Mexico region and which has remained the only uniquely Mexican-American music. The button accordion is the major instrument here, supported by the bajo sexto (an oversized rhythm-bass guitar), drumsand, on occasion, bass and saxophone; two-part vocal harmonies are also mark of the style.

Jimenez' father, Santiago Jimenez, was one of the most important and influential norteno musicians at the time the style was being popularized through radio broadcasts and 78s. Flaco has maintained that popularity through a string of recordings that a bit difficult to find, but highly entertaining and rewarding. "El Rey de Texas" and "A Mis Amigos . . . Carinosamente" (DLB1028 and 1034, respectively) represent his most recent release and are fine introductions to the polka-and-bolera-dominated norteno sound.

The remarkable happy rhythmic flavors stand out here, a logical result of much norteno music being directed to the dance halls that dot the border region. These albums can be ordered from Down Home Music, 10341 San Pablo Avenue, El Cerrito, Calif, 94530, or directly from the manufocturer; DLB Records 527 Highway 90 West, San Antonio, Texas 78237.

For those who might be interested in further explorations of Tex-Mex music, Folk Lyric Records has released seven albums that present an historical overview through reissues of 78s and extensive, well researched booklets. Among the most interesting volumes are "Texas-Merxican Border music, Folk Lyric Records has re-(Folk Lyric 9003) and "Texas-Mexican Border Music - Norteno Accordion" (Folk Lyric 9006). Santiago Jimenez and other extremely influential norteno musicians can be heard to great advantage on the latter album, which also can be ordered from Down Home Music if not available in area record stores.

Finally Cooder's interest in Gabby Pahinui's music has led Warner Brothers to release "The Gabby Pahinui Hawaiian Band, Vol. 1" (BS 3023), recorded 2 1/2 years ago and originally released on the Panini label in Hawaii. Pahinui's presence in Hawaiian music is twofold. Not only is he considered the finest musician to have emerged from the islands, but he also has done a great deal to maintain the island's cultural traditions.

Musically, Pahinui evolved the unique slack-key guitar style, with the strings turned down into open chords and then finger-picked. Both Pahinui and his featured associate, Atta Issacs, are masters and the album is at its strongest when the arrangements are at their most elemental.

Cooder is present on several cuts, always in the background, blending in and letting the native musicians control the situation. On many cuts, songs start off with some strumming, as if the band were an engine warming up before exploding into its joygul gait.

There are some sparkling solos from everyone and melodies are consistently packed with aural and verbal imagery (translations are provided) that evoke a love for nature and the land and an intriguing life of innocence.

This music bears no relationship to Don Ho or Martin Denny and the only sour notes on the album come from Nick DeCaro's totally unnecessary, and happily infrequent, string section intrusions. Otherwise, this is a marvelous, succulent album.

The opening song on Cooder's "Show Time" is "School Is Out," It's obvious, though, from the interest he has generated in these two magnificent regional musicians, and hence in their genre, that for Ry Cooder, school is, in fact, never out.