Once more North American adolescents have an idol. His name is Elvis Presley. And once more the parents of the teenagers are bewildered by it all.

At a Presley concert in San Diego, city police and a detachment of Navy shore patrol were called out to quell an audience of 5,000 squealing youngsters. In Halifax, a radio station banned his recordings because they didn't come up to the station's standards.

Two years ago, Presley was earning $35 a week as a truck driver in Memphis. Last month he picked up $16,000 for one week's singing at a night club.

With his records selling at the rate of 50,000 a day in the United States and a corresponding rate in Canada, Presley is the current phenomenon of the hit-parade world. His records have gone straightto the top in three categories, popular, country and western, and rock'n'roll.

Neither he nor his followers can explain his popularity, although he is not the first performer to arouse similar audience reactions. In the late thirties Benny Goodman had youngsters dancing in the aisles of theatres. In the early forties Frank Sinatra draped himself around a microphone and adolescents swooned.

There'll always be a musical personality to play the Pied Piper, but this time Piper Presley has proved thoroughly bewildering to the adult public. As one baffled man said when he first saw Presley on the Dorsey Brother's TV Stage Show: "I thought it was all a horrible mistake". Like most adults, he instantly disliked Presley's agonized style of singing, his strutting and almost sexual contortions.

Most teen-agers, and especially the girls, take an opposite attitude. They admire Presley's husky six-foot two-inch frame, his babyish, sulky face with the long sideburns. His rather raffish appearance and his youth (he's just 21, which makes him almost one of them) could be two of the reasons for his popularity. He is often described by frantic females as "a living doll".

Aside from his physical attractions, however, it is Presley's singing, halfway between a western and a rock 'n' roll style that has sent teen-agers into a trance.

They like his wailing in a popular song like "Blue Moon" or such western tunes as "I'll Never Let You Go". But they go crazy over the earthy, lusty mood of such rock 'n' roll numbers as "Money Honey". The reason is simple enough: Presley sings with a beat.

It is the beat that predominates in today's hit parade recordings, most noticeably in the rock'n'roll and western tunes - two fields, incidentally, which are rapidly merging. The intrumentalists may be poor and the voices inferior, but throughout each record a strong, infectious rhythm predominates - to such an extent that youngsters are now once more beginning to dance.

Today, the rock'n'roll exponents are giving new life to popular music that for too long has been bogged down with gimmicks. Since the mid-forties, record companies have flooded the market with "trick" records: multiple voicings, echo chambers, noisy vocal quartets. They caught the interest, but not for long.

When the first rock'n'roll records came along the teen-agers took them to their hearts. For the first time in years they discovered they could do more than just sit and listen to records. Now they could dance to them.

Not that rock'n'roll is any better musically than the gimmick records. Most rock'n'roll tunes sound alike. There's a monotonous use of vocal and instrumental combinations, and not even the all-powerful beat can make up for the shortcomings of lyrics and melodies. But these records do make the listeners want to dance.

As a result, youngsters have become almost vehement in their defence of rock'n'roll - and Elvis Presley. Aside from their perennial cry that this music "is new and different", invariably they say, "It's got a beat."

What they don't understand is that Presley's style of singing, especially on up-tempo tunes like "Money Honey", "Tutti Frutti" or "Blue Suede Shoes", is as old as the music of America. It goes back to the days of the first blues singer, the rhythm of the ragtime pianists and the marching bands of New Orleans in the early part of this century.

North Americans have been among the last to recognize the vitality of America's music - a music that has throbbed with rhythm since the days of the blues shouters, the time of the boogie woogie pianists, through the swing and bob eras, right up to today's "introspective" jazz.

Maybe that's why Presley himself can't explain why his music is "different". He did give a revealing glimpse of himself when I recently interviewed him by telephone for the Toronto Telegram. As a child, he said, he spent every free moment listening to the radio in his home town of Tupelo, Mississippi.

"Ah arrived at my style accidentally" he said. "Ah don't know how it happened. But Ah know Ah've listened to religious spirituals all my life. When Ah was a kid Ah would have had the radio on for 24 hours a day if Ah could."

It's no wonder then that Presley sings with a beat. From his childhood on he was absorbing the uninhibited rhythms and vocal mannerisms of the great gospel singers. (Mahalia Jackson and Georgia Peach are two outstanding examples. Some of their numbers, in fact, surpass anything Presley has done from the standpoint of rhythmic intensity and excitement.)

While it might appear that rock'n'roll is an overnight rage, this type of music has been selling for years on race records - a term applied to records sold to Negro audiences in the southern United States during the thirties and forties. These featured blues singers and small bands who emphasized a "rocking" beat. They were, as well, infinitely superior to most of today's commercialized output.

Northern groups added honking tenor saxophones used more sophisticated types of singers. Gradually the records began to appear on disc jockey shows. Teen-agers became aware of the "new" music. Their purchase of recordings made by rock ' n' roll artists hurtled them into the hit parade. The transition had been made.

What is significant about this movement is the fact that radio and records, rather than TV, sent Presley and his ilk to the top. While adult members of families stayed glued to their TV sets, the young ones were listening to their radios.

An 18-year-old girl told me why. "Teenagers have tired of TV," she said. "They are going back to radio and records where they get the music they want when they want it."

It's not surprising that parents recoiled with dismay when they first saw Presley on TV. He was completely beyond their understanding, and they reacted accordingly. As a result, teen-agers now look upon Presley as something more than just an enterntainer. Adults obviously don't want any part of him, so Presley becomes something special in the young people's eyes. They belong, as it were, to an extraordinarily exclusive club. They will defend him to the end. Well, nearly to the end.

Hit parade fans are a fickle lot. In time they'll send Presley off into obscurity, as they are now doing to Johnny Ray. But you can be certain of one thing: there'll always be music with a beat. There will, whether you like it or not, always be an Elvis Presley.