THE MOURNING THOUSANDS who watched the white hearse carry Elvis Presley's body to a mausoleum in Memphis attest to the compelling hold of the "King of Rock" on a substantial segment of American society. Coming from a Mississippi background whose favorite music was white country blues, Elvis - it will not do, even in his obituary, to call him "Mr. Presley" - happened upon the commercial scene in the mid-1950s just as white music was being integrated, if you will, with the earthier, angrier black music of rhythm and blues and a touch of gospel. Not so coincidently, white America was in the throes of its crisis of integration with black America. Elvis Presley became the leading practitioner of the new style, especially in the South, where at his death his week flags flew at half-staff.

He could hardly have solidified his place in the popular culture, however, if another current had not also been running. The national popular music of the period just before his was top-heavy with adult music, often-sentimental moods and songs and singers favored by adults. Elvis unconsciously plugged into the 1950s' budding sense of generation revolt, becoming the hero of many of the young by his readiness to offend their elders.

This he did splendidly: by offering a loud and raucous sound and a sullen public mien, by covering up his naturally pleasant voice with a hard whine, by singing lyrics centered on the concerns of teenagers, especially teenaged love, and most dramatically - to mady adults, most threateningly - by caricaturing sexual movements. His first national television performance (censored, yet below the waist) in 1956 is still remembered, by his fans, as perhaps the most delicious outrage of his career.

Even in later years, when many felt that his performances were imitations of his earlier self, Elvis enjoyed popular success and adulation and riches. He lived a star's pampered self-centered life, occasionally giving Cadillacs to acquaintances, and he died young, at age 42, though he does not seem to have adopted the penchant for self-destruction that rock fans often seem to crave for their heroes. Elvis gave pleasure and a measure of self-worth to a great many people who were, by reason of their region or class or age, in transition. His was no small career.