Digitech, however, have broken away from that idea and are offering units tailored to particular types of use. If these problems with pitch‑shifting have been all too evident in the past, particularly on lower cost devices or multi‑effects units that incorporate pitch‑shifting, then perhaps it has been because each unit has tried to address all pitch‑shifting applications. Subtle pitch‑shifting is great for thickening up a sound, and small amounts can bring a persistently flat vocalist into correct tune (or at least they will waver up and down around the correct pitch rather than always being below it). Even so, there are many occasions where these side‑effects go unnoticed, don't matter, or can be consciously traded against the advantage pitch‑shifting can offer. There will always be some glitching, warbling, or other artifact to give the game away. True, the original product didn't provide perfect pitch‑shifting, and even now with modern technology you can't expect a pitch‑shifted sound to be every bit as good as the original. Then came a company called Eventide, with their famous Harmonizer, which changed all that for good. Pitch‑shifting was once deemed to be an unattainable effect something that everyone wanted, but not really practical to any usable level of quality. David Mellor explores ways to spice up vocal and guitar lines, courtesy of two new Digitech harmony processors.