I'm not sure I have such a fine tuned ear to get it dialed in...
Few people do, until they understand what to listen for. It's not like anyone's born knowing what accurate stylus azimuth sounds like. ;-)
It's actually not a matter of tuning our ears. We each hear what we hear and there's little anyone can do to change it (other than a good cleaning, lol).
What needs training is our brains, our capacity to consciously observe what our senses detect. Holmes and Watson had both trod the steps up to their flat hundreds of times. Yet when the detective asked the doctor exactly how many steps there were, the doctor was unable to say. He'd never paid attention. Holmes of course, had. (There were 18 by the way... those high Victorian ceilings.)
The Wally Shop and Fozgometer work by measuring crosstalk. You then tweak azimuth until crosstalk is equalized between channels and/or minimized (hopefully both, but that is stylus and cartridge dependent).
So, I asked myself, what would minimal or zero crosstalk sound like. Clearly, zero crosstalk would result in R channel information coming *only* from the R speaker and L channel information coming *only* from the L speaker. This would produce the tightest, most precise stereo imaging.
Conversely, excessive crosstalk would spread information across both speakers that was intended to be in one speaker only. How would this sound? Sonic images that should be precise and directional would sound fat, spread wider across the horizontal azis than is natural and difficult to localize.
What kind of sounds would make this most audible? Clearly, the sounds our ears most rely on for directional cues. What are these? Higher frequency sounds, which are more easily pinpointed due to their shorter wavelengths. The shorter the wavelength, the greater the difference (in number of waves) between the timing of the sound's arrival at our two ears. This is how our brain determines the direction of a sound. This is also why the directionality of low frequency sounds is harder to determine, since a long wavelength will reach both ears at almost the same point in the wave.
So, what kind of music should we use for checking azimuth? From the above it's obvious. Choose records with well recorded passages for natural solo instruments or voices in the upper registers. A flute or piccolo, not a contra-bassoon. Ella or Callas, not Robeson or Pavoratti.
Nothing electric or amplified. No one knows how wide a recorded electric guitar should sound. It depends entirely on the speaker setup it was playing out of.
Tweak azimuth in tiny amounts (the smallest adjustment your tonearm allows) until sonic images are as tight as possible from left to right. A flute should sound 1" wide, not three feet. Etc.
Hope this helps. I owned a Wally Analog Shop and it works, but I'd be reluctant to order one now; both for the reason you stated and because, having tried, I trained myself to listen for and adjust azimuth much faster and just as accurately without it.
