FILMING ELVIS
A sequence in "Blue Hawaii," Hal Wallis Production for Paramount, calls for a quartet of beachboys in an outrigger to sing a number as Elvis Presley swims out to meet their canoe while cameras grind from the nearby shore.
The problem was to synchronise the quartet's singing and rhythmic paddle strokes with the play-back on the beach - too far away for the sound to carry above surf noises.
It was solved by choreographer Charles O'Curran and cable man Jerry DeVore, with two walkie-talkies, one suspended in front of the play-back loud speaker, the other lashed out of sight inside the canoe, where it picked up the pre-recorded number perfectly.
Elvis Monthly July 1961
http://www.youtube.com/watch?v=O9tcFh6Qa5M