Perhaps one of the best scenes in "The Buddy Holly Story" is when Gary Busey as Holly takes his girlfriend to lover's lane in his father's pickup. When they get there, however. Holly is more interested in the radio than his amorous companion. He fiddles anxiously with the dial till he finds it: a black rhythm & blues station bouncing in from some warp in the ionosphere. Holly, the awkward white teen-ager from smalltown Texas listens to the Five Satins sing "In the Still of the Night" as if it were a transmission from Mars, a broadcast from the promised land.

Similar scenes are recounted in the biographies of Elvis Presley, Bob Dylan and Bob Seger. There are stories of the Beatles and Rolling Stones buying imported American rhythm & blues records as teen-agers and trying to duplicate the sound themselves. Throughout rock'n' roll runs the theme of white teen-agers entranced by the urgency of black rhythm & blues, who dream of making that sound themselves.

What better model could there be than Otis Redding and the quartet that backed him -- Booker T. & the M.G.s. Redding sang with all the immense pleasure and emotion of southern soul at its best. And though half the M.G.s turned out to be white, the foursome played with a compressed energy that was the essence of black R&B. What dream could be sweeter than to sing with the M.G.s as if you were Redding himself?

That is just what John Belushi and Dan Aykroyd are doing as the Blues Brothers. The band on their album, "Briefcase Full of Blues" (Atlantic SD 19217), mcludes two of the three living M.G.s: guitarist Steve Cropper and bassist Donald "Duck" Dunn. The album opens and closes with Redding's signature theme, "I Can't Turn You Loose," and includes another M.G.-backed hit, "Soul Man."

"Briefcase Full of Blues" is both a parody or white musicians imitating the blues and a legitimate extension of that tradition. Originally a skit on NBC's "Saturday Night Live," Belushi and Aykroyd exaggerated white stereotypes by dressing as mafia goons and dancing like bureaucrats unexpectedly unchained from their chairs.

But apparently their own high regard for the blues got the upper hand over the parody. They hired the best R&B musicians in Los Angeles. Paul Shaffer fills in perfectly for Booker T. on organ, and guitarist Matt Murphy plays like the three blues Kings -- B.B.., Albert and Freddie. Fusion saxophonist Tom Scott joing a trio of veteran R&B hornplayers: Tom Malone Lou Marini and Alan Rubin. Many of these musicians have been on the best R&B records ever made and they play the same way here.

Belushi betrays his record collector habits by passing up the obvious tunes for obscure items by jump blues singers Floyd Dixon and Joe Turner. "Rubber Biscuit" was a 1956 non-hit for the Chips known only to fanatical R&B collectors (the gibberish is rumored to be based on a reform school chant.)

Belushi, who first made his reputation with his spastic Joe Cocker imitations, takes all the lead vocals but one. He proves a capable blues singer; nothing extraordinary, but no embarrassment to this first-rate band. His few ventures out of middle range are shaky, but mostly he stays at a comfortable pitch and growls with the requisite passion.

Levon Helm, the Band's drummer, did the Blues Brothers one better on his first solo album, "Levon Helm and the R.C.O. Allstars" (ABC AA;1017) He fulfilled everyone's dream by actually joining Booker T. & the M.G.s. Helm filled the chair of deceased drummer Al Jackson and played R&P chestnuts with Cropper, Dunn and Booker T. Jones.

Unfortunately, the music isn't as impressive as the credits Like too many all-star sessions, the players sound uncomfortable with each other. On his new album, "Levon Helm" (ABC AA-1089), however, Helm defers to Dunn as producer, and the songs crackle with the old M.G.s' fire.

Everything is filed down to basic requirements. Cropper's clipped rhythm guitar and sparse fills nail the Muscle Shoals Rhythm Band to "the beat" at its most fundamental. The Malone- Marini-Rubin horns are just as focused, reinforcing the rhythm for the climaxes.

All this frees Helm's gravelly Arkansas voice. That voice once made the Band's "The Night They Drove Ol' Dixie Down" sound as if it came straight from an overgrown Confederate cemetery. None of the songs on the new album are that substantial, but Helm sings the R&B party songs with a similar authenticity -- as if he had led the same house band at the same backwoods roadhouse for generations.

Since Otis Redding died in a plane crash in 1967, the southern soul singer that everyone has fantasized about has been Al Green. Within the past six months, three versions of his old song, "Take Me to the River," have appeared: on the Talking Heads' "More Songs About Buildings and Food" (Sire SRK 6058); on Bryan Ferry's "The Bride Stripped Bare" (Atlantic SD 19205), AND ON "Levon Helm."

The best cover vrsion is Helm's. He barks out the title plea as if he has been carried away by the need. Ferry and the Heads' David Byrne sing as if they're still looking for the need, for any need, for any emotion.

When Redding bowled one over with a ferocious baritone, Green seduces one with a transparent tenor. No other singer can harmonize with himself without dubbing the way Green can. He will float a melody only to slip out below it for a low harmony, jump back on and then leap without the slightest trace of effort into a parallel falsetto.

Green's genius is his ability to sing in a totally relaxed and relaxing mood, but at the same time skip all over several octaves for one musical surprise after another. This combination of reassuring intimacy and constant surprise can be intoxicatingly erotic or ecstatically religious.

Green is now the pastor of his own "Full Gospel Tabernacle" in Tennessee. But his current religious themes can still be heard as erotic, just as his earlier romantic themes could be heard as holy.

"Truth N' Time" (Hi HLP 6009) is Green's second album as producer and guitarist, but unlike the superior 1977 classic, "The Belle Album" (Hi HLP 6004), only three of the songs are his. The single is "To Sir With Love," the theme from the Sidney Poitier movie. Dedicating it to his father, Green turns the simply ditty into a moving tribute to parenthood. His wispy voice drifts back into memories and then gathers into a trilling upward spiral for the chorus.

All eight songs become delightfully unpredictable, because one never knows where Green's voice is going next. Perhaps the best song is "Blow Me Down" by Green's guitarist, Bernard Staton. With wry couplets like "Staying legal/Is hard without the eagle," the lyrics advise spiritual optimism in the face of the world's trials. But no words could match the optimism of Green's parenthetical "oohs" and "ahs." Here is a song that could set a suburban teen-ager dreaming of imitation.

"Briefcase Full of Blues" never reaches the musical heights of "Levon Helm," much less "Truth N' Time,' but the Blues Brothers will outsell Helm and Green exponen tially. This too is in keeping with the tradition of white singers imitating the blues. Copies with a show business angle have always outsold the original masterpieces.

Belushi and Aykroyd can hardly be considered villains, though. They have imitated faithfully and well, giving due credit to all their sources. "Briefcase Full of Blues" is bound to create more interest (and sales) in the original blues singer than would have existed otherwise, just as British rock bands once created more work for Muddy Waters. This too is part of the tradition.