Most people know Glen Campbell was a hot-shot guitar player in L.A. in the '60's. He played on hundreds of sessions, for The Beach Boys, Phil Spector, Quincy Jones and other top producers, as part of the famous Wrecking Crew. Here's another side of his session work, as a demo vocalist. Those were the singers hired to do trial run recordings so the stars would have an idea of what the song should sound like before they laid down their vocals.
Campbell did that work for songwriter Ben Weisman, who was a quiet force in pop music, the composer of hundreds of tunes from 1949 on. Most significantly, he wrote 57 songs recorded by Elvis, the most of any songwriter. He was the kind of writer for hire who could compose for specific projects or artists, and had the right style for Elvis, plus was able to knock 'em off for films, which was where the King was at in the '60's. Writing with lyricist Sid Wayne, he came up with the title songs for movies such as Clambake, Stay Away Joe and Spinout.
If you know your Elvis, this wasn't the best of his material. They were catchy and memorable, but lightweight. It's more interesting hearing Campbell putting Elvis-style energy into the songs. On the track There Is So Much World To See, from Double Trouble, Campbell at times sounds exactly like Presley. On others, his country twang comes through and his voice is instantly recognizable, but he does through in some Elvis-like yeah's. He certainly wasn't mocking Presley, the two were friends and the respect is obvious. He's trying his best, even with dubious cuts such as Do The Clam.