Ever since George Martin overdubbed everything from tape loops and backwards effects to whole orchestras on The Beatles' songs, popular music has relied pretty heavily on what's called "ear candy" to entice the listeners' ears.

Today's PC-based recording programs, popular with home recordists, are capable of all of the ear candy that George Martin had at his disposal — and then some. But it's always worthwhile to revisit the tricks of the past, and add them to our modern-day sonic palettes. And along the way notice that what was cutting edge back then has been surpassed by a whole new level of technological advancement.

Enter The Harmonizer

Beginning in the mid-1970s, an increasingly popular way to add lots of ear candy to a recording was with a product created by the Eventide H910, the first of a line of Eventide, Inc.'s rack-mounted effects under their Harmonizer brand name (which has since become a registered trademark of Eventide). Led Zeppelin loved this product so much that live, they ran Robert Plant's vocals through a Harmonizer (the slightly later H949 model, apparently) on certain songs, to allow him to sing harmonies with himself. Jimmy Page installed one in his equipment rack to use it on his guitar solos.

But it was on recordings that the Harmonizer made its true mark. On Coda, Zeppelin's 1982 swan song, John Bonham's drum solo "Bonzo's Montreux" was extensively treated by Page with a Harmonizer to make Bonham sound like he was playing steel drums and a battery of other tuned percussion. David Bowie used it on "Fame" for the bits where the song's title seems to swoop up and down in pitch. When asked by Bowie how the Harmonizer works, Tony Visconti, his producer replied that "it f***s with the fabric of time!'"

Well, it's not quite at that level of science fiction. But the harmonizer does sample the audio that's fed into it, and after a virtually imperceptible lag time of a few milliseconds, it spits it out at a higher or lower pitch.

And it doesn't have to be a full octave or third or fifth higher or lower than the original vocal. Because while the original Eventide Harmonizer sounds pretty funky transposing vocals when they're that far beyond the original pitch (though its not as bad with instruments, as we'll discuss in a moment), it does a great job of doubling vocals, when it's used for much more subtle effects.

Two recent VST plug-ins for PC recording programs illustrate the alpha and the omega of electronic harmony generators.